Bias domain

Source of bias

Possible answers

Selection

(1) Was the method of randomisation adequate?

Yes/no/unsure

Selection

(2) Was the treatment allocation concealed?

Yes/no/unsure

Performance

(3) Was the patient blinded to the intervention?

Yes/no/unsure

Performance

(4) Was the care provider blinded to the intervention?

Yes/no/unsure

Detection

(5) Was the outcome assessor blinded to the intervention?

Yes/no/unsure

Attrition

(6) Was the drop‐out rate described and acceptable?

Yes/no/unsure

Attrition

(7) Were all randomized participants analysed in the group to which they were allocated?

Yes/no/unsure

Reporting

(8) Are reports of the study free of suggestion of selective outcome reporting?

Yes/no/unsure

Selection

(9) Were the groups similar at baseline regarding the most important prognostic indicators?

Yes/no/unsure

Performance

(10) Were co‐interventions avoided or similar?

Yes/no/unsure

Performance

(11) Was the compliance acceptable in all groups?

Yes/no/unsure

Detection

(12) Was the timing of the outcome assessment similar in all groups?

Yes/no/unsure

Other

(13) Are other sources of potential bias unlikely?

Yes/no/unsure

1

A random (unpredictable) assignment sequence. Examples of adequate methods are coin toss (for studies with 2
groups), rolling a dice (for studies with 2 or more groups), drawing of balls of different colours, drawing of
ballots with the study group labels from a dark bag, computer‐generated random sequence, preordered
sealed envelopes, sequentially‐ordered vials, telephone call to a central office, and preordered list of
treatment assignments.Examples of inadequate methods are: alternation, birth date, social insurance/security number, date in which
they are invited to participate in the study, and hospital registration number.

2

Assignment generated by an independent person not responsible for determining the eligibility of the patients.
This person has no information about the persons included in the trial and has no influence on the
assignment sequence or on the decision about eligibility of the patient.

3

Index and control groups are indistinguishable for the patients or if the success of blinding was tested among
the patients and it was successful.

4

Index and control groups are indistinguishable for the care providers or if the success of blinding was tested
among the care providers and it was successful.

5

Adequacy of blinding should be assessed for each primary outcome separately. This item should be scored
ʺyesʺ if the success of blinding was tested among the outcome assessors and it was successful or:

‐ for patient‐reported outcomes in which the patient is the outcome assessor (e.g., pain, disability): the blinding
procedure is adequate for outcome assessors if participant blinding is scored ‘‘yes’’
‐ for outcome criteria assessed during scheduled visit and that supposes a contact between participants and
outcome assessors (e.g., clinical examination): the blinding procedure is adequate if patients are blinded, and
the treatment or adverse effects of the treatment cannot be noticed during clinical examination
‐ for outcome criteria that do not suppose a contact with participants (e.g., radiography, magnetic resonance
imaging): the blinding procedure is adequate if the treatment or adverse effects of the treatment cannot be
noticed when assessing the main outcome
‐ for outcome criteria that are clinical or therapeutic events that will be determined by the interaction between
patients and care providers (e.g., cointerventions, hospitalization length, treatment failure), in which the care
provider is the outcome assessor: the blinding procedure is adequate for outcome assessors if item ‘‘4’’
(caregivers) is scored ‘‘yes’’
‐ for outcome criteria that are assessed from data of the medical forms: the blinding procedure is adequate if
the treatment or adverse effects of the treatment cannot be noticed on the extracted data

6

The number of participants who were included in the study but did not complete the observation period or
were not included in the analysis must be described and reasons given. If the percentage of withdrawals and
drop‐outs does not exceed 20% for short‐term follow‐up and 30% for long‐term follow‐up and does not lead
to substantial bias a ‘‘yes’’ is scored. (N.B. these percentages are arbitrary, not supported by literature).

7

All randomized patients are reported/analyzed in the group they were allocated to by randomization for the
most important moments of effect measurement (minus missing values) irrespective of noncompliance and
cointerventions.

8

All the results from all prespecified outcomes have been adequately reported in the published report of the
trial. This information is either obtained by comparing the protocol and the report, or in the absence of the
protocol, assessing that the published report includes enough information to make this judgment.

9

Groups have to be similar at baseline regarding demographic factors, duration and severity of complaints,
percentage of patients with neurological symptoms, and value of main outcome measure(s).

10

If there were no cointerventions or they were similar between the index and control groups.

11

The reviewer determines if the compliance with the interventions is acceptable, based on the reported
intensity, duration, number and frequency of sessions for both the index intervention and control
intervention(s). For example, physiotherapy treatment is usually administered for several sessions; therefore it
is necessary to assess how many sessions each patient attended. For single‐session interventions (e.g.,
surgery), this item is irrelevant.

12

Timing of outcome assessment should be identical for all intervention groups and for all primary outcome
measures.

13

Other types of biases. For example:
‐ When the outcome measures were not valid. There should be evidence from a previous or present scientific
study that the primary outcome can be considered valid in the context of the present.
‐ Industry‐sponsored trials. The conflict of interest (COI) statement should explicitly state that the researchers
have had full possession of the trial process from planning to reporting without funders with potential COI
having any possibility to interfere in the process. If, for example, the statistical analyses have been done by a
funder with a potential COI, usually ʺunsureʺ is scored.

Postoperative braces versus no postoperative braces for adults with degenerative lumbar diseases

Patient or population: adults with degenerative lumbar disease

Settings: postoperative of degenerative lumbar disease

Intervention: with postoperative braces

Comparison: without postoperative braces

Outcomes

Outcome type

(continuous/

dichotomous)

Outcome measure

Comments

Function

Continuous

Oswestry Disabilty Index (ODI), Roland‐Morris Questionnaire (RMQ)

medium‐term

Back pain

Continuous

Visual Analogue Scale (VAS)

medium‐term

Quality of life

Continuous

SF‐36 questionnaire

medium‐term

Use of analgesic medications

Dichotomous

Yes/no

short‐term

Postoperative complications

Dichotomous

Yes/no

medium‐term

Return to work

Dichotomous

Yes/no

long‐term

GRADE Working Group grades of evidence
High quality: further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: we are very uncertain about the estimate.

Short‐term: less than 3 months after surgery

Medium‐term: 3 to 6 months after surgery

Long‐term: greater than 6 months after surgery