Overall prognosis of preschool autism spectrum disorder diagnoses

Amanda Brignell; Rachael C Harwood; Tamara May; Susan Woolfenden; Alicia Montgomery; Alfonso Iorio; Katrina Williams

doi:10.1002/14651858.CD012749.pub2

Pronóstico global de los diagnósticos de trastorno del espectro autista en edad preescolar

Appendices

Appendix 1. Search strategies

Ovid MEDLINE

12 October 2017 (7283 records)
5 July 2021 (3916 records)

1 child development disorders, pervasive/
2 asperger syndrome/
3 autism spectrum disorder/
4 autistic disorder/
5 autis$.tw.
6 asperger$.tw.
7 pervasive development$ disorder$.tw.
8 (child$ adj3 pervasiv$).tw.
9 (PDD adj3 (specified or unspecified)).tw.
10 PDD‐NOS.tw.
11 or/1‐10
12 prognosis/
13 prognos$.tw,kf.
14 prevalence/
15 prevalenc$.tw,kf.
16 follow up studies/
17 (follow$ up$ or followup$).tw.
18 ((diagnos$ or temporal$) adj3 (change$ or stable or unstable or reliab$ or stabili#e$ or stability or instability or re‐evaluat$)).tw,kf.
19 ((developmental or diagnos$) adj1 (outcome$ or trajector$)).tw.
20 (diagnos$ adj1 (baseline or base‐line or early or earlier or first or improve$ or improving or initial$ or original$ or previous$)).ab.
21 (diagnos$ adj1 (final or second or later or subsequent$)).ab.
22 (outcome$ adj2 (change$ or improve$ or severe or severity or trajector$ or worse or worst or worsen$)).ab.
23 (symptom$ adj2 (change$ or improve$ or improving or reduc$ or severe or severity or trajector$ or worse or worst or worsen$)).ab.
24 ((measure$ or score$ or rating$) adj2 (change$ or improve$ or improving or severe or severity or worse or worst or worsen$)).ab.
25 predict$.ab,kf.
26 or/12‐25
27 11 and 26
28 ((autis$ or asperger$ or pervasive) and (improve$ or improving or stability or stable)).ti.
29 27 or 28 [Final line of 2017 search]
30 (201710* or 2018* or 2019* or 2020* or 2021*).dt,ez,da.
31 29 and 30
32 remove duplicates from 31 [Final line of 2021 search]

Ovid Epub Ahead of Print (via Ovid MEDLINE(R) and Epub Ahead of Print, In‐Process, In‐Data‐Review & Other Non‐Indexed Citations, Daily and Versions(R))

12 October 2017 (412 records)
5 July 2021 (413 records)

1 autis$.tw.
2 asperger$.tw.
3 pervasive development$ disorder$.tw,kf.
4 (child$ adj3 pervasiv$).tw,kf.
5 (PDD adj3 (specified or unspecified)).tw,kf.
6 PDD‐NOS.tw,kf.
7 or/1‐6
8 prognos$.tw,kf.
9 prevalenc$.tw,kf. )
10 (follow$ up$ or followup$).tw,kf.
11 ((diagnos$ or temporal$) adj3 (change$ or stable or unstable or reliab$ or stabili#e$ or stability or instability or re‐evaluat$)).tw,kf.
12 ((developmental or diagnos$) adj1 (outcome$ or trajector$)).tw,kf.
13 (diagnos$ adj1 (baseline or base‐line or early or earlier or first or initial$ or original$ or previous$)).ab.
14 (diagnos$ adj1 (final or second or later or subsequent$)).ab.
15 (outcome$ adj2 (change$ or improve$ or improving or severe or severity$ or trajector$ or worse or worst or worsen$)).ab.
16 (symptom$ adj2 (change$ or improve$ or improving or reduc$ or severe or severity$ or trajector$ or worse or worst or worsen$)).ab.
17 ((measure$ or score$ or rating$) adj2 (change$ or improve$ or improving or severe or severity$ or worse or worst or worsen$)).ab.
18 predict$.ab,kf.
19 or/8‐18
20 7 and 19
21 ((autis$ or asperger$ or pervasive) and (improve$ or improving or stability or stable)).ti.
22 20 or 21
23 limit 22 to publisher

Ovid MEDLINE In‐Process, In‐Data‐Review & Other Non‐Indexed Citations (via Ovid MEDLINE(R)) and Epub Ahead of Print, In‐Process, In‐Data‐Review & Other Non‐Indexed Citations, Daily and Versions(R)

2 October 2017 (1296 records)
5 July 2021 (1457 records)

1 autis$.tw.
2 asperger$.tw.
3 pervasive development$ disorder$.tw,kf.
4 (child$ adj3 pervasiv$).tw,kf.
5 (PDD adj3 (specified or unspecified)).tw,kf.
6 PDD‐NOS.tw,kf.
7 or/1‐6
8 prognos$.tw,kf.
9 prevalenc$.tw,kf.
10 (follow$ up$ or followup$).tw,kf.
11 ((diagnos$ or temporal$) adj3 (change$ or stable or unstable or reliab$ or stabili#e$ or stability or instability or re‐evaluat$)).tw,kf.
12 ((developmental or diagnos$) adj1 (outcome$ or trajector$)).tw,kf.
13 (diagnos$ adj1 (baseline or base‐line or early or earlier or first or initial$ or original$ or previous$)).ab.
14 (diagnos$ adj1 (final or second or later or subsequent$)).ab.
15 (outcome$ adj2 (change$ or improve$ or improving or severe or severity or trajector$ or worse or worst or worsen$)).ab.
16 (symptom$ adj2 (change$ or improve$ or improving or reduc$ or severe or severity or trajector$ or worse or worst or worsen$)).ab.
17 ((measure$ or score$ or rating$) adj2 (change$ or improve$ or improving or severe or severity$ or worse or worst or worsen$)).ab.
18 predict$.ab,kf.
19 or/8‐18
20 7 and 19
21 ((autis$ or asperger$ or pervasive) and (improve$ or improving or stability or stable)).ti.
22 20 or 21
23 limit 22 to ("in data review" or in process or "pubmed not medline") [Annotation: Final line 2017]
24 (201710* or 2018* or 2019* or 2020* or 2021*).dt,ed,ez.
25 23 and 24 [Annotation: Final line 2021]

Embase Ovid

12 October 2017 (8263 records)
5 July 2021 (4452 records)

1 *autism/ or *asperger syndrome/ or *childhood disintegrative disorder/ or *"pervasive developmental disorder not otherwise specified"/
2 autis$.tw.
3 asperger$.tw.
4 pervasive development$ disorder$.tw.
5 (pervasive adj3 child$).tw.
6 PDD‐NOS$.tw.
7 or/1‐6
8 *prognosis/
9 prognos$.tw,kw.
10 *follow up/
11 (follow$ up$ or followup$).tw.
12 ((diagnos$ or temporal$) adj3 (change$ or improve$ or stable or unstable or reliab$ or stabili#e$ or stability or instability or re‐evaluat$)).tw.
13 ((developmental or diagnos$) adj1 (outcome$ or trajector$)).tw.
14 (diagnos$ adj1 (baseline or base‐line or early or earlier or first or initial$ or original$ or previous$)).ab.
15 (diagnos$ adj1 (final or second or later or subsequent$)).ab.
16 (outcome$ adj2 (change$ or improve$ or improving or severe or severity or trajector$ or worse or worst or worsen$)).ab.
17 (symptom$ adj2 (baseline or change$ or improve$ or improving or reduc$ or severe or severity or trajector$ or worse or worst or worsen$)).ab.
18 ((measure$ or score$ or level$) adj2 (baseline or change$ or improve$ or improving or severe or severity or worse or worst or worsen$)).ab.
19 (predict$ adj3 (baseline or change$ or course or reduc$ or severe or severity or trajector$ or worse or worst or worsen$)).ab.
20 predict$.kw.
21 or/8‐20
22 7 and 21
23 ((autis$ or asperger$ or pervasive) and (improve$ or improving or stability or stable)).ti.
24 22 or 23 [Annotation: Final line 2017]
25 limit 24 to yr="2017 ‐Current"
26 remove duplicates from 25 [Annotation: Final line 2021]

CINAHL Plus EBSCOhost

12 October 2017 (3260 records)
6 July 2021 (2070 records)

S1 (MM "Child Development Disorders, Pervasive")
S2 (MM "Autistic Disorder")
S3 (MM "Asperger Syndrome")
S4 (MM "Pervasive Developmental Disorder‐Not Otherwise Specified")
S5 TI(autis*) or AB (autis*)
S6 TI(asperger*) or AB (asperger*)
S7 TI (pervasive development* disorder*) OR AB (pervasive development* disorder*)
S8 TI (child* N3 pervasiv*) OR AB (child* N3 pervasiv*)
S9 TI ( (PDD N3 (specified or unspecified)) ) OR AB ( (PDD N3 (specified or unspecified)) )
S10 TI PDD‐NOS OR AB PDD‐NOS
S11 S1 OR S2 OR S3 OR S4 OR S5 OR S6 OR S7 OR S8 OR S9 OR S10
S12 (MM "Prognosis")
S13 TI prognos* OR AB prognos*
S14 (MH "Prospective Studies+")
S15 TI ( "follow up" or follow‐up ) OR AB( "follow up" or follow‐up )
S16 TI ( ((developmental or diagnos*) N1 (outcome* or trajector*)) ) OR AB ( ((developmental or diagnos*) N1 (outcome* or trajector*)) )
S17 TI ( ((diagnos* or temporal*) N3 (change* or stable or unstable or reliab* or stabili* or stability or instability or re‐evaluat*)) ) OR AB ( ((diagnos* or temporal*) N3 (change* or stable or unstable or reliab* or stabili* or instability or re‐evaluat*)) )
S18 AB (diagnos* N1 (baseline or base‐line or early or earlier or first or initial* or original* or previous*))
S19 AB (diagnos* N1 (final or second or later or subsequent*))
S20 AB (outcome* N2 (change* or improve* or improving or severe or severity or trajector* or worse or worst or worsen*))
S21 AB (symptom* N2 (change* or improve* or improving or reduc* or severe or severity or trajector* or worse or worst or worsen*))
S22 AB ((measure* or score* or rating*) N2 (change* or improve* or improving or severe or severity or worse or worst or worsen*))
S23 AB predict*
S24 S12 OR S13 OR S14 OR S15 OR S16 OR S17 OR S18 OR S19 OR S20 OR S21 OR S22 OR S23
S25 S11 AND S24
S26 TI ((autis* or asperger* or pervasive) and (improve* or improving or stability or stable))
S27 S25 OR S26 [Annotation: Final line 2017]
S28 EM 20171001‐
S29 S27 AND S28 [Annotation: Final line 2021]

APA PsycINFO OVID

12 October 2017 (7476 records)
5 July 2021 (3286 records)

1 autism spectrum disorders/
2 autis$.tw.
3 asperger$.tw.
4 pervasive development$ disorder$.tw.
5 (child$ adj3 pervasiv$).tw.
6 (PDD adj3 (specified or unspecified)).tw.
7 PDD‐NOS.tw.
8 or/1‐7
9 prognosis/
10 prognos$.tw.
11 disease course/
12 "severity (disorders)"/
13 (follow$ up$ or followup$).tw.
14 ((diagnos$ or temporal$) adj3 (change$ or stable or unstable or reliab$ or stabili#e$ or stability or instability or re‐evaluat$)).tw.
15 ((developmental or diagnos$) adj1 (outcome$ or trajector$)).tw.
16 (diagnos$ adj1 (baseline or base‐line or early or earlier or first or initial$ or original$ or previous$)).ab.
17 (outcome$ adj2 (change$ or improve$ or improving or sever$ or trajector$ or worse or worst or worsen$)).ab.
18 (symptom$ adj2 (change$ or improve$ or improving or reduc$ or sever$ or trajector$ or worse or worst or worsen$)).ab.
19 ((measure$ or score$ or rating$) adj2 (change$ or improve$ or improving or sever$ or worse or worst or worsen$)).ab.
20 predict$.ab.
21 or/9‐20
22 8 and 21
23 ((autis$ or asperger$ or pervasive) and (improve$ or improving or stability or stable)).ti.
24 22 or 23 [Annotation: Final line 2017]
25 limit 24 to up=20171001‐20210628
26 remove duplicates from 25 [Annotation: Final line 2021]

Conference Proceedings Citation Index‐Science (CPCI‐S) and Conference Proceedings Citation Index‐Social Sciences & Humanities (CPCI‐SSH) (searched via Web of Science Clarivate)

12 October 2017 CPCI‐S (328 records) CPCI‐SSH (47 records)
6 July 2021 CPCI‐S (273 records) CPCI‐SSH (4 records)
#17 #12 OR #11
Indexes=CPCI‐SSH Timespan=2017‐2021 [Annotation: Final line 2021]
# 16 #12 OR #11
Indexes=CPCI‐S Timespan=2017‐2021 [Annotation: Final line 2021]
#15 #12 OR #11
Indexes=CPCI‐SSH Timespan=All years [Annotation: Final line 2017]
# 14 #12 OR #11
Indexes=CPCI‐S Timespan=All years [Annotation: Final line 2017]
#12 TI=((autis* or asperger* or pervasive) and (improve* or improving or stability or stable))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#11 #10 AND #1
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#10 #9 OR #8 OR #7 OR #6 OR #5 OR #4 OR #3 OR #2
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#9 TS=((measure* or score* or rating*) Near/1 (change* or improve* or improving or severe* or severity or worse or worst or worsen*))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#8 TS=(symptom* Near/1 (change* or improve* or improving or severe* or severity or reduc* or trajector* or worse or worst or worsen*))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#7 TS=(outcome* Near/1 (change* or improve* or improving or severe* or severity or trajector* or worse or worst or worsen*))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#6 TS=(diagnos* Near/1 (final or second or later or subsequent*))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#5 TS=(diagnos* Near/1 (baseline or base‐line or early or earlier or first or initial* or original* or previous*)
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#4 TS=((diagnos* or temporal*) Near/3 (change* or stable or unstable or reliab* or stabili*e* or stability or instability or re‐evaluat*) )
Indexes=CPCI‐S, CPCI‐SSHTimespan=All years
#3 TS=((developmental or diagnos*) Near/1 (outcome* or trajector*)
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#2 TS=(prognosis* or followup or "follow‐up" or "follow* up" or predict*)
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years
#1 TS=( autis* or asperger* or PDD OR "PDD‐NOS" OR PERVASIVE NEAR/1 (DISORDER* OR CHILD*) ))
Indexes=CPCI‐S, CPCI‐SSH Timespan=All years

Cochrane Database of Systematic Reviews (in the Cochrane Library)

12 October 2017 (4 records)
6 July 2021 (3 records)

#1 MeSH descriptor: [Child Development Disorders, Pervasive] explode all trees
#2 (autis* or asperger*):ti
#3 (PDD N3 (specified or unspecified)):ti or "pervasive development* disorder*":ti or PDD next NOS:ti
#4 {or #1‐#3}
#5 (prognos* or diagnos* or predict*):ti
#6 #4 and #5, in Cochrane Reviews, Cochrane Protocols
#7 #4 and #5 with Cochrane Library publication date Between Oct 2017 and Jul 2021, in Cochrane Reviews, Cochrane Protocols

Database of Reviews of Abstracts of Effectiveness (DARE) in the Cochrane Library

12 October 2017 (2 records)

#1 MeSH descriptor: [Child Development Disorders, Pervasive] explode all trees
#2 (autis* or asperger*):ti
#3 (PDD N3(specified or unspecified)) or "pervasive development* disorder*" or PDD next NOS:ti
#4 {or #1‐#3}
#5 (prognos* or diagnos* or predict*):ti
#6 #4 and #5

Epistemonikos (www.epistemonikos.org)

12 October 2017 (21 records)
6 July 2021. Limited to records added between 1 October 2017 and 6 July 2021 (4 records)

title:((autis* OR asperger* OR PDD* OR "pervasive disorder" OR "pervasive development") AND ( predict* OR prognos* OR stabil* OR stable OR trajectory )) OR (title:((autis* OR asperger* OR PDD* OR "pervasive disorder" OR "pervasive development") AND ("diagnostic stability" OR "stable diagnosis")) OR abstract:((autis* OR asperger* OR PDD* OR "pervasive disorder" OR "pervasive development") AND ("diagnostic stability" OR "stable diagnosis")))
Systematic review filter applied.

SciELO (Scientific Electronic Library Online)

17 November 2021 (493 records)

(autis* or pervasiv* or asperger*) AND (prognos* or diagnos* or predict*)

NIHR (National Institute for Health Research)

17 November 2021 (30 records)

autis*; pervasive; asperger*

Clarivate Web of Science forward citations search

17 November 2021 (990 records)

We completed forward citation searches for all included studies.

Appendix 2. Data collection spreadsheet

Column heading	Definition
Study number	‐
Author	First author (surname and first initial)
Country of publication	‐
Year of publication	‐
Description of study	Study description, prospective cohort, retrospective cohort, assessment of outcome, controlled, with/without intervention, aim of the study
Study population/group	Clinic versus population versus clinical drawn from a broad population base
Sampling frame	Description of where sample was collected from
Study sample	Description of baseline study sample
Inclusion/exclusion criteria	Participants that were eligible for study are described
Adequacy of participation	Adequacy of participation in the study by all who were eligible
Size of population/group	Number (N) at baseline, denominator for proportion analyses; proportion (%) male
Diagnostic criteria	DSM; ICD; or Kanner and edition number
Diagnostic tool/measure at baseline and follow‐up	ADI‐R; ADOS; CARS; GARS; 3di; or DISCO
Consistency of tool	Same diagnostic tool for all; same method and setting of outcome for all participants; whether valid reliable tool; completeness of outcome measure
Timing of diagnosis	Prior to study, at baseline, etc.
Multidisciplinary assessment	Diagnosis was completed by two or more professionals
Diagnosis	AD; ASD; AD + PDD‐NOS; as defined by diagnostic criteria
Age at baseline in years	‐
Age at follow‐up in years	‐
Period of follow‐up in years	Length of follow‐up for the study
Cognitive ability/IQ	Outcome; measure used
Language ability	Outcome; measure used
Adaptive behaviour ability	Outcome; measure used
Study approach and outcomes	When outcomes were measured
Numerator for primary outcome	Number diagnosed with ASD at follow‐up
Denominator for primary outcome	Number assessed for ASD at follow‐up
Proportion continuing to meet diagnostic criteria	Numerator divided by denominator
Autistic symptoms ‐ core	Outcome: social communication/repetitive, restricted behaviours, and interests; measure used
Autistic symptoms ‐ other	Outcome: what symptoms or measure used
Study attrition	Number of participants lost to follow‐up; participants that did not complete all parts of follow‐up or tools; reasons for loss to follow‐up; whether reasons have been linked to outcome
Interventions	Type and amount of interventions
Groups	Control group versus intervention group
Notes	‐
Footnotes AD: autistic disorder; ADI‐R: Autism Diagnostic Interview ‐ Revised; ADOS: Autism Diagnostic Observation Schedule;ASD: autism spectrum disorder; CARS: Childhood Autism Rating Scale; DISCO: Diagnostic Interview for Social and Communication Disorders; DSM: Diagnostic and Statistical Manual of Mental Disorders;GARS: Gilliam Autism Rating Scale;ICD: International Classification of Diseases;IQ: intelligence quotient; PDD‐NOS: pervasive developmental disorder‐not otherwise specified; 3di: developmental, dimensional and diagnostic interview.

Appendix 3. Description of risk of bias criteria and the criteria for assigning judgements

1. Study participation: the study sample adequately represents population of interest
Criteria	Unclear	High	Moderate	Low
Sample (described)	‐	Clinical (not community based)	Clinical but drawn from broad community base	Population based
Description of sampling frame	‐	Not described	Some description but not adequate or complete	Well described
Description of baseline study sample	‐	Not described	Some description but not adequate or complete	Well described
Description of inclusion or exclusion criteria	‐	Not described	Some description but not adequate or complete	Well described
Adequacy of participation in study by all eligible	‐	No	‐	Yes
2. Study attrition: the study data available (those not lost to follow‐up) adequately represent the study sample
Criteria	Unclear	High	Moderate	Low
Recruitment	‐	Retrospective	Retrospective with whole cohort considered	Prospective
LFU (%)	‐	< 80% remain	≥ 80% remain	≥ 85% remain
Description of attempts to collect information on those LFU	‐	No	Some information provided but not adequate	Yes
Reasons for LFU provided?	‐	No	Some information provided but not adequate	Yes
Reasons for LFU linked to outcome?	‐	No	Some information provided but not adequate	Yes
Adequate description of LFU participants?	‐	No	Some information provided but not adequate	Yes
Analysis: important differences between LFU and non‐LFU in study?	‐	Important differences	‐	No important differences
3. Outcome measurement: the outcomes of interest are measured in a similar way for all participants
Criteria	Unclear	High	Moderate	Low
Blinding	‐	Not blinded	Blinding inadequate	Blinding adequate
Clear definition of outcome provided?	‐	No	‐	Yes
Same outcome tool for all?	‐	Not same tool for all	‐	Same for all
Valid and reliable tool?	‐	Not valid, reliable tool used	Valid or reliable tool, but parent rating	Standardised, reliable, valid tool used
Method and setting of outcome measurement same for all participants?	‐	No	‐	Yes
Completeness of outcome measure	‐	Not all tools completed (> 90% missing)	Not all tools completed but not > 90% missing	All tools completed
Footnotes LFU: Loss to follow‐up.

Appendix 4. GRADE assessment for judging the overall quality of the evidence for prognosis

In grading the quality of the evidence we considered observational studies starting as high quality.

	Domain	Description
Rate down if:	Risk of bias	The overall quality is driven by the study with lowest quality (if only low risk of bias studies are use, then the quality is rated as high ; individual studies are rated down one or two levels for serious or critical risk of bias.
	Inconsistency	Unexplained heterogeneity or variability in results (point estimates) across studies with differences in estimates exceeding decisional thresholds. Large I² value (significant heterogeneity) and visual inspection of the forest plot (effect sizes on either side of the lines of no effect and with confidence intervals showing little to no overlap) usually prompt concerns around heterogeneity
	Indirectness	The study sample or the outcomes in the study, or both, do not accurately reflect the population of interest or the measured outcome does not capture what is believed to be important
	Imprecision	This is based primarily the position of the confidence interval relative to a clinical decision threshold
	Publication bias	Forrest plot or statistical testing suggesting that small negative studies are underrepresented
Rate up if:	Large effect	Moderate or large effect reported by most studies or in pooled findings in the meta‐analysis
Rate up if:	Dose‐response gradient	Gradient exists between studies for factors measured at different doses or an increase or decrease in events over time, which follows a well‐defined pattern (e.g. linear)
Footnotes Table modified from Guyatt 2011, Hayden 2014 and Iorio 2015.

Appendix 5. Levels of quality

Quality level	Definition
High	We are very confident that the true prognosis (probability of future events) lies close to that of the estimate
Moderate	We are moderately confident that the true prognosis (probability of future events) is likely to be close to the estimate, but there is a possibility that it is substantially different
Low	Our confidence in the estimate is limited: the true prognosis (probability of future events) may be substantially different from the estimate
Very low	We have very little confidence in the estimate: the true prognosis (probability of future events) is likely to be substantially different from the estimate
Footnotes This table has been reproduced from Iorio 2015, with permission from the first author.

Appendix 6. Methods for future updates and unused methods

Unit of analysis issues

In future updates of this review, we may be required to complete some data manipulation if continuous scores rather than dichotomised categories are presented for diagnostic groups.

Dealing with missing data

In future reviews, if indicated, we will assess the sensitivity of any primary analyses to missing data using the strategy described in the Cochrane Handbook for Systematic Reviews of Interventions (Deeks 2022). That is, we will perform sensitivity analyses to assess how sensitive the results are by excluding studies if they present data requiring transformations with uncertain assumptions or where they contain a large amount of missing data. We were unable to complete this analysis for primary analyses as the only data we analysed were where all cases were followed up. Therefore, there were no missing data in primary analyses.

Assessment of reporting biases

The very small number of studies that were rated at low risk of bias precluded sensitivity analyses for this review. If future updates have more studies with low risk of bias ratings we will conduct sensitivity analyses to assess the impact of risk bias on outcome.

Data synthesis

If, in future updates of the review included studies are found to be more homogenous than expected, we will analyse the data using a fixed‐effect model.

Prognostic factor analyses

We planned to complete analyses of prognostic factors on studies that used the same or different versions or editions of the diagnostic tool at baseline and follow‐up, or on autism spectrum disorder subgroups (i.e. autistic disorder versus pervasive developmental disorder ‐ not otherwise specified). However, due to the small number of studies that had presented data for these areas we were not able to complete these analyses. We may be able to complete this analysis in future updates.

Sensitivity analysis

In future updates of this review, if there are additional studies with low risk of bias ratings, we will use sensitivity analyses to assess the impact of our decisions made during the review (e.g. inclusion of studies in the review and risk of bias of studies, taking into account recruitment, blinding and outcome measurement factors). This will be achieved by repeating the analyses using an alternative method or assumption, in order to explore the influence of our risk of bias assessments; for example, by the exclusion of lower‐quality studies (those at high or unclear risk of bias due to study participation, participant attrition or outcome measurement).

Appendix 7. Forest plots

a) Forest plot of diagnostic stability by age at baseline

Figure 6

Age at baseline: < 2 years; 2 to 3 years; 4 to 6 years; 7 to 12; years; 13 to 17 years

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and age at baseline.

b) Forest plot of diagnostic stability by age at follow‐up

Figure 7

Age at follow up: 2 to 3 years; 4 to 6 years; 7 to 12 years; 13 to 18 years

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and age at follow‐up.

c) Forest plot of diagnostic stability by duration of follow‐up

Figure 8

Duration of follow‐up: short‐term (up to 2 years), medium‐term (2 to 5 years), and long‐term (6 to 17 years) follow‐up

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and duration of follow‐up.

d) Forest plot of diagnostic stability by decade of publication

Figure 9

Decade of publication: 1960 to 1969; 1970 to 1979; 1980 to 1989; 1990 to 1999; 2000 to 2009; 2010 to 2019

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and decade of publication.

e) Forest plot of diagnostic stability by mean intelligence quotient

Figure 10

Intelligence: mean IQ 70; mean IQ > 70; or more than 70% of the cohort has IQ 70

Footnote
CI: confidence interval; ES: effect size; IQ: intelligence quotient; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and mean intelligence quotient.

f) Forest plot of diagnostic stability by language ability

Figure 11

Language: > 70% verbal; > 70% non‐verbal (i.e. use < 15 words); mean standardised language score < 70; mean standardised language score 70; or > 70% of the cohort has mean language score < 70

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and language ability.

g) Forest plot of diagnostic stability by adaptive behaviour

Figure 12

Adaptive behaviour: mean standard score 70; mean standard score > 70; or > 70% of the cohort has mean standard score 70

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and adaptive behaviour ability.

h) Forest plot of diagnostic stability by multidisciplinary diagnosis

Figure 13

Multidisciplinary team used for diagnosis, Yes or No

Footnote
CI: confidence interval; ES: effect size; N: number in sample

There was no significant association between the proportion of children who continued to meet diagnostic criteria for autism spectrum disorder at follow‐up and whether the diagnosis involved a multidiciplinary team or not.

Appendix 8. Key characteristics of included studies

Variable		Not included in meta‐analysis (n = 8)		Included in meta‐analysis (n = 34)
Variable		n	%	n	%
Year published	Older (< 2013)	3	38	18	53
Year published	Recent (2013‐2021)	5	62	16	47
Tools used to diagnose autism spectrum disorder	One tool	8	100	21	62
	Two tools	0	0	10	29
	Three tools +	0	0	3	9
Multidisciplinary approach		0^a	0	13^b	45
Autism subgroup	Autism spectrum disorder	6	100	32	94
	Autistic disorder	0	0	2	6
	Childhood autism	0	0	0
IQ	< 70	4^c	80	15^d	58
	> 70	0	0	9	35
	Mixed	1	20	2	7
Male		433	80	9139	82
Sample size mean (range)		67 (13‐272)		329^e (11‐8564)
Age at baseline in years mean (range)		3.81 (2.5‐4.9)		3.04 (1.13‐5)
Length of follow‐up in years mean (range)		4.24 (1‐7.36)		2.53 (1‐8.3)
Risk of bias (rated low)	Sample (clinical, clinical from broad base, population)	0	0	4	12
	Description of sampling frame	2	25	9	26
	Description of baseline study sample	4	50	15	44
	Description of inclusion or exclusion criteria	3	38	14	41
	Adequacy of participation in study by all eligible	3	38	15	44
	Recruitment (prospective)	7	88	22	65
	Loss to follow‐up (LFU; low= >85% retained)	5	63	13	38
	Description of attempts to collect info on those LFU	0	0	3	9
	Reasons for LFU provided	0	0	3	9
	Reasons for LFU linked to outcome	1	13	1	3
	Description of LFU participants	0	0	1	3
	Analysis: important differences LFU vs non‐LFU in study	2	25	6	18
	Blinding	1	13	5	15
	Clear definition of diagnosis	6	75	33	97
	Same diagnosis outcome tool for all	8	100	34	100
	Valid and reliable tool	8	100	34	100
	Method and setting of outcome measurements same for all participants	4	50	21	62
	Completeness of outcome measure	7	88	33	97
IQ: intelligence quotient; n: number.
Footnotes LFU: Loss to follow‐up. ^an = 3 ^bn = 29 ^cn = 3 ^dn = 26 ^eIf we remove the outlier study with n = 8564, mean n = 79.

Appendix 9. Justifications for risk of bias assessments across 18 criteria

Study ID: Baghdadli 2012
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	51% of sample lost to follow‐up
Description of attempts to collect information on those LFU	Moderate	Some information provided but inadequate
Reasons for LFU provided	Low	Yes
Reasons for LFU linked to outcome	Moderate	Some information provided but inadequate
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Low	No
Blinding	Moderate	Inadequately blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Benedettto 2021
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	High	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	13% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Bopp 2006
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect info on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Brian 2016
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	High	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	29% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Low	No
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Chu 2017
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	13% of sample lost to follow‐up
Description of attempts to collect info on those LFU	High	Not described
Reasons for LFU provided	High	Not described
Reasons for LFU linked to outcome	High	Not described
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Demb 1989
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	High	Not described
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	33.3% of sample lost to follow‐up
Description of attempts to collect information on those LFU	Moderate	Some information but information inadequate
Reasons for LFU provided	Moderate	Some information but information inadequate
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	No
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No, 11 were done in person and one via phone
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: DeWaay 2012
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up but participants selected retrospectively from a prospective cohort
Description of attempts to collect info on those LFU	Unclear	Not described
Reasons for LFU provided	Unclear	Not described
Reasons for LFU linked to outcome	Unclear	Not described
Description of LFU participants	Unclear	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	High	No
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Eaves 2004
Domain	Risk of bias level	Support for judgement
Sample (described)	Low	Population‐based sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Unclear	Not discussed
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Elmose 2014
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Moderate	Retrospective, with the whole cohort considered
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Low	Yes
Reasons for LFU provided	Moderate	Some information but information is inadequate
Reasons for LFU linked to outcome	High	Not described
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	High	Not described
Blinding	Low	Blinding adequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Flanagan 2011
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Freeman 2004
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	Moderate	Blinding inadequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Gillberg 1990
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	High	Not
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Moderate	Valid or reliable but parent‐rated tool
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Giserman‐Kiss
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU	Not described
Reasons for LFU provided	Not applicable as no LFU	Not described
Reasons for LFU linked to outcome	Not applicable as no LFU	Not described
Description of LFU participants	Not applicable as no LFU	Not described
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU	Not described
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Gonzalez 1993
Domain	Risk of bias level	Support for judgement
Sample (described)	Low	Population‐based sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Moderate	Retrospective with the whole cohort considered
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Haglund 2020
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	2% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	Low	Blinding adequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Hinnebusch 2017
Domain	Risk of bias level	Support for judgement
Sample (described)	Low	Population‐based sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	44% of sample lost to follow‐up
Description of attempts to collect information on those LFU	Low	Yes
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	Unclear	Not described
Description of LFU participants	Low	Yes
Analysis: important differences LFU vs non‐LFU in study	Low	Some differences but these would not impact outcome
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	High	More than 90% of diagnostic tools not completed

Study ID: Kim 2015
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Not described
Description of inclusion or exclusion criteria	Low	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Klintwall 2015
Domain	Risk of bias level	Support for judgement
Sample (described)	Unclear	Not described
Description of sampling frame	Moderate	Some description
Description of baseline study sample	High	Not described
Description of inclusion or exclusion criteria	Moderate	Some
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Mahli 2011
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	54.2% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	Unclear	Not described
Description of LFU participants	Moderate	Some information but inadequate
Analysis: important differences LFU vs non‐LFU in study	Low	Yes
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Moore 2003
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	% of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Low	Blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Moss 2008
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Low	Participation in study by all eligible was adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Moderate	20% of sample lost to follow‐up
Description of attempts to collect information on those LFU	Low	Well described
Reasons for LFU provided	Low	Yes
Reasons for LFU linked to outcome	Low	Yes
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Low	Yes
Blinding	Moderate	Blinding inadequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Ozonoff 2015
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Low	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	High	Not described
Blinding	Low	Blinding adequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Paul 2008
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Moderate	Blinding inadequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Qian 2018
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	HIgh	Not described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Moderate	Some described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Rivard 2019
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	HIgh	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	High	Inadequate participation in study by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up but selected participants retrospectively from a prospective cohort
Description of attempts to collect information on those LFU	Unclear	Not described
Reasons for LFU provided	Unclear	Not described
Reasons for LFU linked to outcome	Unclear	Not described
Description of LFU participants	Unclear	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not described
Clear definition of diagnosis provided at follow‐up	High	No
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Robain 2020
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	High	No
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Sheinkopf 1998
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	High	Not described
Description of baseline study sample	High	Not described
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Moderate	Retrospective, with the whole cohort considered
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Moderate	Not all tools completed but not > 90% missing

Study ID: Smith 2019
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	48% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	Low	Yes
Reasons for LFU linked to outcome	Moderate	Some information provided but inadequate
Description of LFU participants	Moderate	Some information provided but inadequate
Analysis: important differences LFU vs non‐LFU in study	Low	No important differences reported
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Moderate	Not all tools completed but not >90% missing

Study ID: Soke 2011
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Not described
Description of inclusion or exclusion criteria	Low	Not described
Adequacy of participation in study by all eligible	Low	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	22% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	All tools complete

Study ID: Solomon 2014
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	25% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	Unclear	Not described
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	All tools complete

Study ID: Solomon 2016
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	47% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	Low	Yes
Reasons for LFU linked to outcome	Moderate	Some information but inadequate
Description of LFU participants	Moderate	Some information but inadequate
Analysis: important differences LFU vs non‐LFU in study	Low	No
Blinding	Low	Blinding adequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	All tools complete

Study ID: Spjut Jansson 2016
Domain	Risk of bias level	Support for judgement
Sample (described)	Low	Population based sample
Description of sampling frame	Low	Well described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	High	Participation in study by all eligible not adequate
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Moderate	Blinding inadequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	High	No
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Sullivan 2010
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	High	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	Moderate	Retrospective with the whole cohort considered
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	All tools complete

Study ID: Szatmari 2021
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a brand community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	High	Not described
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	28% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	Low	Yes
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	High	Yes, important differences reported
Blinding	HIgh	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	High	No
Completeness of outcome measure	Low	Diagnostic tools completed by all study participants

Study ID: Takeda 2007
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Blinding inadequate
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Thomas 2009
Domain	Risk of bias level	Support for judgement
Sample (described)	Unclear	Not described
Description of sampling frame	High	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect info on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Venker 2014
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Low	Well described
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	High	Not described
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	High	20.2% of sample lost to follow‐up
Description of attempts to collect information on those LFU	High	Not described
Reasons for LFU provided	High	No
Reasons for LFU linked to outcome	High	No
Description of LFU participants	High	Not described
Analysis: important differences LFU vs non‐LFU in study	High	Yes
Blinding	Unclear	Not described
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Unclear	Not described
Completeness of outcome measure	Low	All tools complete

Study ID: Wu 2016
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Unclear	Not described
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Moderate	Valid or reliable but parent rated
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Zappella 1990
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	High	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Unclear	Not described
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Zappella 2010
Domain	Risk of bias level	Support for judgement
Sample (described)	High	Clinical sample
Description of sampling frame	High	Not described
Description of baseline study sample	Moderate	Some description
Description of inclusion or exclusion criteria	Moderate	Some description
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	High	Retrospective
Loss to follow‐up (LFU)	Not applicable as the study is retrospective
Description of attempts to collect information on those LFU	Not applicable as the study is retrospective
Reasons for LFU provided	Not applicable as the study is retrospective
Reasons for LFU linked to outcome	Not applicable as the study is retrospective
Description of LFU participants	Not applicable as the study is retrospective
Analysis: important differences LFU vs non‐LFU in study	Not applicable as the study is retrospective
Blinding	High	Not blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Unclear	Not described
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Study ID: Zwaigenbaum 2016
Domain	Risk of bias level	Support for judgement
Sample (described)	Moderate	Clinical sample from a broad community base
Description of sampling frame	Moderate	Some description
Description of baseline study sample	Low	Well described
Description of inclusion or exclusion criteria	Low	Well described
Adequacy of participation in study by all eligible	Low	Adequate participation in study by all eligible
Recruitment	Low	Prospective
Loss to follow‐up (LFU)	Low	None of sample lost to follow‐up
Description of attempts to collect information on those LFU	Not applicable as no LFU
Reasons for LFU provided	Not applicable as no LFU
Reasons for LFU linked to outcome	Not applicable as no LFU
Description of LFU participants	Not applicable as no LFU
Analysis: important differences LFU vs non‐LFU in study	Not applicable as no LFU
Blinding	Low	Adequately blinded
Clear definition of diagnosis provided at follow‐up	Low	Yes
Same diagnosis outcome tool for all	Low	Yes
Valid and reliable tool	Low	Standardised, reliable valid tool used
Method and setting of outcome measurements same for all participants	Low	Yes
Completeness of outcome measure	Low	All tools complete

Footnotes

LFU: loss to follow up; vs: versus

Appendix 10. Funnel Plot

Figure 14

Funnel Plot of included studies

Figure 1

Study flow diagram.

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Figure 2

Risk of bias ratings on the QUIPS tool (40 studies). Green is low risk of bias, orange is moderate risk of bias and red is high risk of bias.

Summary risk of bias ratings for provided for each QUIPS domain (i.e.study participation, study attrition, outcome measurement). See Appendix 9 for a figure showing all criteria that were rated for each domain. Studies were rated to have an overall low risk of bias if all three summary domains were rated low or moderate risk of bias. Studies were rated to have an overall high risk of bias if all three summary domains were rated low or moderate risk of bias.

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Figure 3

Risk of bias graph: review authors' judgements about each risk of bias item for each included study presented as percentages across all included studies (41 studies).

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Figure 4

Risk of bias ratings for each included study for each of the 18 criteria. Red indicates high, orange indicates moderate, green indicates low and yellow indicates unclear risk of bias.

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Figure 5

Forest plot of proportion of children that retained their autism diagnosis

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 6

Age at baseline: < 2 years; 2 to 3 years; 4 to 6 years; 7 to 12; years; 13 to 17 years

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 7

Age at follow up: 2 to 3 years; 4 to 6 years; 7 to 12 years; 13 to 18 years

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 8

Duration of follow‐up: short‐term (up to 2 years), medium‐term (2 to 5 years), and long‐term (6 to 17 years) follow‐up

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 9

Decade of publication: 1960 to 1969; 1970 to 1979; 1980 to 1989; 1990 to 1999; 2000 to 2009; 2010 to 2019

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 10

Intelligence: mean IQ 70; mean IQ > 70; or more than 70% of the cohort has IQ 70

Footnote
CI: confidence interval; ES: effect size; IQ: intelligence quotient; N: number in sample

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Figure 11

Language: > 70% verbal; > 70% non‐verbal (i.e. use < 15 words); mean standardised language score < 70; mean standardised language score 70; or > 70% of the cohort has mean language score < 70

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 12

Adaptive behaviour: mean standard score 70; mean standard score > 70; or > 70% of the cohort has mean standard score 70

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 13

Multidisciplinary team used for diagnosis, Yes or No

Footnote
CI: confidence interval; ES: effect size; N: number in sample

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Figure 14

Funnel Plot of included studies

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Summary of findings 1. Summary of findings

Proportion of individuals who have a diagnosis of autism spectrum disorder at baseline and continue not meet diagnostic criteria at follow‐up one or more years later

Patient or population: children diagnosed with autism spectrum disorder

Settings: range of settings

Outcomes

Relative effect

(95% CI)

Number of participants

(studies)

Quality of the evidence
(GRADE)

Comments

Proportion with an autism spectrum disorder diagnosis at baseline and follow‐up

Follow‐up: > 12 months

0.92

(0.89 to 0.95)

11,105 (34 studies:

1 intervention trial with 1 arm;

1 RCT^a;

2 non‐RCTs^a;

30 TAU or in the community)

⊕⊕⊝⊝

Low^b,c

Limitations (ROB): serious^b

Inconsistency: serious^c

Indirectness: not serious

Imprecision: not serious

Publication/reporting bias: not serious

Effect size: N/A

Dose response gradient: N/A

Confirmatory evidence: N/A

See footnotes below.

Social communication at baseline and follow‐up (mean score)

Follow‐up: > 12 months

See comments

None of the included studies provided separate domain scores at baseline and follow‐up

Restricted and repetitive behaviours and interests at

baseline and follow‐up (mean score)

Follow‐up: > 12 months

See comments

None of the included studies provided separate domain scores at baseline and follow‐up

Defnitions of levels of evidence

High: We are very confident that the true prognosis (probability of future events) lies close to that of the estimate

Moderate: We are moderately confident that the true prognosis (probability of future events) is likely to be close to the estimate, but there is a possibility that it is substantially different

Low: Our confidence in the estimate is limited: the true prognosis (probability of future events) may be substantially different from the estimate

Very low: We have very little confidence in the estimate: the true prognosis (probability of future events) is likely to be substantially different from the estimate

CI: Confidence intervals;N/A: Not applicable;RCT(s): Randomised controlled trial(s);ROB: Risk of bias; TAU: Treatment as usual.

^aData were taken from the control arm of the study
^bWe downgraded the quality of the evidence by one level for risk of bias due to high risk of bias across most studies: 85% of studies were rated moderate or high risk of bias in study participation, 68% were moderate or high risk of bias in study attrition and 88% were rated moderate or high risk of bias for outcome measurement. Only 5% of studies were rated low risk of bias across all three criteria.
^cWe downgraded the quality of the evidence one level for inconsistency of results (large heterogeneity (I² = 88.71%), P value (P < 0.01)). The forest plot showed significant variation between point estimates for studies and non‐overlapping confidence intervals across many studies. The least and most optimistic point estimates varied considerably (60% to 100%) and each of these estimates were likely to result in different conclusions about the stability of a diagnosis in autism spectrum disorder.

Summary of findings 1. Summary of findings

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Table 1. Changes to the classification systems over time

Year published	Classification system	Subgroups (as specified in the classification system)
1975	International Classification of Diseases, Ninth Revision, Clinical Modification (ICD‐9‐CM)	Autistic disorder
1980	Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM‐III)	PDD: infantile autism, childhood onset PDD and atypical PDD
1987	Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM‐III‐R)	PDD: autistic disorder, PDD‐not otherwise specified (PDD‐NOS)
1994 to 2000	Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM‐IV)	Asperger’s disorder, autistic disorder, PDD‐NOS
1996	International Classification of Diseases, Tenth Revision (ICD‐10)	Childhood autism, Asperger's syndrome, atypical autism, pervasive developmental disorder (PDD) ‐ unspecified
2000 to 2013	Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM‐IV‐TR)	Asperger’s disorder, autistic disorder, PDD‐NOS
2013 to current	Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM‐5)	Autism spectrum disorder
2018	International Classification of Diseases, Eleventh Revision (ICD‐11)	Autism spectrum disorder
PDD‐NOS: pervasive developmental disorder

Table 1. Changes to the classification systems over time

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Table 2. Studies that had multiple publications

Primary publication	Additional publications from the same study
Anderson 2009^a	Anderson 2007, Bedford 2016, Gotham 2012, Gotham 2011, Hus 2011, Lord 1995, Lord 2004, Lord 2012, Luyster 2007, Pickles 2014, Richler 2010, Thurm 2007
Baghdadli 2012	Baghdadli 2018, Baghdadli 2008, Baghdadli 2007, Darrou 2010, Pry 2011, Pry 2012
Bopp 2006	Bopp 2009; Smith 2007
Flanagan 2010	Flanagan 2012
Giserman‐Kiss 2020	Giserman‐Kiss 2018
Moss 2008	Magiati 2007, Magiati 2011a, Magiati 2011b
Qian 2018	Ke 2017, Li 2019
Rivard 2019	Mello 2018
Solomon 2014	Mahoney 2016
Solomon 2016	Solomon 2018, Waizbard‐Bartov 2021
Szatmari 2021	Baribeau 2020, Baribeau 2021, Courchesne 2021, Bennett 2014, Bennett 2015, Georgiades 2014, Georgiades 2021, Szatmari 2015
Venker 2014	Ellis‐Weismer 2015, Davidson 2017, Ray‐Subramanian 2012, Venker 2016
^aMet inclusion criteria but unable to extract data for synthesis as children without a diagnosis of autism spectrum disorder were also included in the cohort. Authors were contacted but we were unable to obtain required data.

Table 2. Studies that had multiple publications

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Table 3. Characteristics of individual studies included in synthesis (n = 34)

Study	Diagnosis type	N at baseline (% male)	IQ (mean standard score)^a	Adaptive behavior (mean standard score)^a	Language (mean standard score)^a	Age at baseline (years)	Follow‐up duration (years)	Diagnostic tool used at baseline (multidisciplinary or not)	Proportion who met diagnostic criteria at follow‐up
Baghdadli 2012	ASD	152 (82)	< 70	< 70	NR	4.90	3.00	ICD‐10 & CARS (Y)	1.0
Benedetto 2021	ASD	147 (80)	NR	NR	NR	2.3	1	DSM‐5 and ADOS (Y)	0.73
Brian 2016	ASD	18 (72)	> 70	NR	> 70	3.15	6.36	DSM‐IV‐TR & ADOS (N)	0.94
Demb 1989	ASD	12 (75)	< 70	NR	NR	4.50	5.00	DSM‐III & DSM‐III R (N)	0.83
Eaves 2004	ASD	43 (80)	< 70	< 70	NR	2.75	2.25	DSM‐IV, CARS, MDT (Y)	0.93
Elmose 2014	ASD	23 (78)	NR	NR	NR	3.10	8.30	ICD‐10, ADOS (Y)	1.00
Flanagan 2010	ASD	67 (82)	NR	< 70	NR	3.59	1.38	CARS (N)	0.81
Freeman 2004	ASD	59 (81)	< 70	NR	NR	4.00	2.2	DSM IV, CARS (N)	0.97
Gillberg 1990	ASD	25 (68)	< 70	NR	NR	1.13	4.04	DSM‐III‐R (N)	0.92
Giserman‐Kiss 2020	ASD	60 (87)	<70	NR	<70	2.31	1.98	ADOS	0.883
Gonzalez 1993	ASD	30 (73)	< 70	NR	NR	4.50	1.00	DSM‐III, DSM‐III‐R, DSM‐IV and ICD 10 (N)	0.97
Hinnebusch 2017	ASD	219 (81)	Both	NR	< 70	2.13	2.16	DSM‐IV, ADOS, CARS (N)	0.83
Kim 2016	ASD	100 (84)	> 70	Both	NR	1.80	1.30	ADOS (Y)	0.93
Klintwall 2015	ASD	70 (89)	> 70	> 70	< 70	1.83	1.36	ADOS G, ADOS T (U)	0.93
Malhi 2011	ASD	77 (83)	< 70	NR	NR	2.48	1.65	CARS (Y)	0.95
Moore 2003	ASD	19 (80)	> 70	NR	< 70	2.83	1.59	ADI‐R (Y)	1.00
Moss 2008	ASD	35 (91)	< 70	< 70	< 70	3.5	7.00	ADI‐R (N)	0.80
Ozonoff 2015	ASD	79 (NR)	NR	NR	NR	2	1	ADI‐R, DSM IV, best clinical estimate (N)	0.82
Paul 2008	ASD	37 (NR)	> 70	> 70	< 70	1.82	1.09	ADOS (Y)	1.00
Qian 2018	ASD	37 (86)	<70	NR	NR	2.57	2	DSM IV TR; CARS ADI‐R (N)	1.00
Robain 2020	ASD	60 (100)	>70	NR	NR	3	1	DSM 5 ADOS (N)	1.00
Santocchi 2012	ASD	98 (NR)	NR	NR	NR	3.25	1.75	ADOS, CARS	0.86
Sheinkopf 1998	ASD	11 (NR)	< 70	NR	NR	2.94	1.51	DSM‐III (Y)	1.00
Soke 2011	AD	28 (79)	< 70	NR	NR	2.75	2.08	ADI‐R (Y)	0.89
Solomon 2014	ASD	55 (84)	< 70	NR	NR	4.21	1.00	ADOS (U)	0.78
Solomon 2016	ASD	102 (80)	> 70	Both	Both	2.86	2.76	ADOS (N)	0.95
Spjut Jansson 2016	ASD	71 (79)	Both	Both	NR	3.03	2.00	ADOS, DISCO, ADI‐R (Y)	0.93
Sullivan 2010	ASD	75 (83)	< 70	< 70	NR	3.94	2.18	CARS (N)	0.53
Takeda 2007	ASD	126 (81)	< 70	NR	NR	2.62	2.90	ICD‐10, CARS (N)	1.00
Venker 2014	ASD	129 (87)	> 70	> 70	Both	2.80	5.85	DSM‐IV, ADOS (Y)	1.00
Wu 2016	ASD	8564 (83)	NR	NR	NR	3.67	1.43	DSM‐IV‐TR file record review (N)	0.91
Zappella 1990	AD	15 (87)	> 70	Both	NR	4.50	1.83	DSM‐III (N)	0.60
Zappella 2010	ASD	534 (84)	NR	NR	NR	5.00	2.67	DSM‐IV‐TR (U)	0.93
Zwaigenbaum 2015	ASD	23 (69)	NR	> 70	NR	1.50	1.50	DSM‐IV‐TR (N)	0.83
^aMean score (IQ, adaptive behaviour or language) for the cohort is < 70 or more than 70% are less than 70. If cohort evenly spread this is signified 'both'. AD: autistic disorder; ADI: Autism Diagnostic Interview;ADOS: Autism Diagnostic Observation Schedule; ASD: autism spectrum disorder; CARS: Childhood Autism Rating Scale; DISCO: Diagnostic Interview for Social and Communication Disorders; DSM: Diagnostic Statistical Manual of Mental Disorders; ICD: International Classification of Diseases; IQ: intelligence quotient; N: no; NR: not reported; PDD‐NOS: pervasive developmental disorder‐ not otherwise specified; U: unclear; Y: yes.

Table 3. Characteristics of individual studies included in synthesis (n = 34)

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Table 4. Prognostic factor analyses (eight comparisons), with effect sizes and confidence intervals

Domain		Relative effect (95% CIs)	No. of participants (studies)	I²
Age at baseline	0 to 2 years	0.94 (0.88 to 0.98)	251 (5 studies)	52.64%, P = 0.08
	2 to 3 years	0.92 (0.88 to 0.95)	9989 (22 studies)	90.17%, P < 0.01
	4 to 5 years	0.91 (0.76 to 0.99)	152 (5 studies)	90.48%, P < 0.01
	5 to 6 years	0.93 (0.90 to 0.95)	534 (1 study)	‐
Age at follow‐up	< 4 years	0.89 (0.79 to 0.96)	443 (6 studies)	86.80%, P < 0.01
	4 to 6 years	0.92 (0.88 to 0.95)	9794 (21 studies)	87.88%, P < 0.01
	7 to 12 years	0.96 (0.89 to 1.00)	868 (7 studies)	88.18%, P < 0.01
Duration of follow‐up	1 to 2 years	0.91 (0.88 to 0.94)	10,745 (27 studies)	87.86%, P < 0.01
	2 to 5 years	0.99 (0.92 to 1.00)	293 (4 studies)	78.16%, P < 0.01
	6 to 17 years	0.92 (0.77 to 1.00)	67 (3 studies)	‐
Decade of publication	1980 to 1989	0.83 (0.55 to 0.95)	12 (1 studies)	‐
	1990 to 1999	0.91 (0.74 to 1.00)	82 (4 studies)	73.16% P = 0.01
	2000 to 2009	0.98 (0.93 to 1.00)	479 (7 studies)	80.57% P < 0.01
	2010 to 2019	0.90 (0.87 to 0.93)	10,273 (19 studies)	86.84% P < 0.01
	2020 to 2029	0.90 (0.68 to 1.00)	259 (3 studies)	‐
Intelligence^a	< 70	0.93 (0.85 to 0.98)	793 (15 studies)	90.88%, P < 0.01
	> 70	0.97 (0.92 to 1.00)	502 (9 studies)	77.54%, P < 0.01
	Both < 70 and > 70	0.86 (0.81, 0.89)	289 (2 studies)	‐
Language^a	< 70	0.92 (0.84 to 0.98)	382 (6 studies)	79.65%, P < 0.01
	> 70	0.94 (0.74 to 0.99)	18 (1 study)	‐
	Both	0.98 (0.96 to 1.00)	205 (2 studies)	‐
Adaptive behaviour^a	< 70	0.85 (0.60 to 0.99)	300 (5 studies)	96.33%, P < 0.01
	> 70	0.97 (0.8 to 1.00)	233 (4 studies)	83.28%, P < 0.01
	Both	0.91 (0.82, 0.97)	283 (4 studies)	73.88%, P = 0.01
Multidisciplinary assessment	Yes	0.97 (0.91 to 1.00)	767 (13 studies)	87.97%, P < 0.01
Multidisciplinary assessment	No	0.88 (0.83 to 0.93)	9468 (16 studies)	89.46%, P < 0.01
^aMean score (IQ, adaptive behaviour or language) for the cohort is < 70 or more than 70% are less than 70. If cohort was evenly spread this is signified 'both'. CI: confidence interval;I²: a statistic that describes the percentage of variation across studies; No.: number.

Table 4. Prognostic factor analyses (eight comparisons), with effect sizes and confidence intervals

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Appendices

Appendix 1. Search strategies

Ovid MEDLINE

Ovid Epub Ahead of Print (via Ovid MEDLINE(R) and Epub Ahead of Print, In‐Process, In‐Data‐Review & Other Non‐Indexed Citations, Daily and Versions(R))

Ovid MEDLINE In‐Process, In‐Data‐Review & Other Non‐Indexed Citations (via Ovid MEDLINE(R)) and Epub Ahead of Print, In‐Process, In‐Data‐Review & Other Non‐Indexed Citations, Daily and Versions(R)

Embase Ovid

CINAHL Plus EBSCOhost

APA PsycINFO OVID

Conference Proceedings Citation Index‐Science (CPCI‐S) and Conference Proceedings Citation Index‐Social Sciences & Humanities (CPCI‐SSH) (searched via Web of Science Clarivate)

Cochrane Database of Systematic Reviews (in the Cochrane Library)

Database of Reviews of Abstracts of Effectiveness (DARE) in the Cochrane Library

Epistemonikos (www.epistemonikos.org)

SciELO (Scientific Electronic Library Online)

NIHR (National Institute for Health Research)

Clarivate Web of Science forward citations search

Appendix 2. Data collection spreadsheet

Appendix 3. Description of risk of bias criteria and the criteria for assigning judgements

Appendix 4. GRADE assessment for judging the overall quality of the evidence for prognosis

Appendix 5. Levels of quality

Appendix 6. Methods for future updates and unused methods

Unit of analysis issues

Dealing with missing data

Assessment of reporting biases

Data synthesis

Prognostic factor analyses

Sensitivity analysis

Appendix 7. Forest plots

Appendix 8. Key characteristics of included studies

Appendix 9. Justifications for risk of bias assessments across 18 criteria

Appendix 10. Funnel Plot

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