Aislamiento como estrategia para el control de la transmisión de la infección por virus de la hepatitis C (HCV) en unidades de hemodiálisis
Appendices
Appendix 1. Electronic search strategies
| Database | Search terms |
| CENTRAL |
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| MEDLINE |
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| EMBASE |
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Appendix 2. Risk of bias assessment tool
| Potential source of bias | Assessment criteria |
| Random sequence generation Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence | Low risk of bias: Random number table; computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots; minimization (minimization may be implemented without a random element, and this is considered to be equivalent to being random). |
| High risk of bias: Sequence generated by odd or even date of birth; date (or day) of admission; sequence generated by hospital or clinic record number; allocation by judgement of the clinician; by preference of the participant; based on the results of a laboratory test or a series of tests; by availability of the intervention. | |
| Unclear: Insufficient information about the sequence generation process to permit judgement. | |
| Allocation concealment Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment | Low risk of bias: Randomisation method described that would not allow investigator/participant to know or influence intervention group before eligible participant entered in the study (e.g. central allocation, including telephone, web‐based, and pharmacy‐controlled, randomisation; sequentially numbered drug containers of identical appearance; sequentially numbered, opaque, sealed envelopes). |
| High risk of bias: Using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate safeguards (e.g. if envelopes were unsealed or non‐opaque or not sequentially numbered); alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure. | |
| Unclear: Randomisation stated but no information on method used is available. | |
| Blinding of participants and personnel Performance bias due to knowledge of the allocated interventions by participants and personnel during the study | Low risk of bias: No blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken. |
| High risk of bias: No blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; blinding of key study participants and personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding. | |
| Unclear: Insufficient information to permit judgement | |
| Blinding of outcome assessment Detection bias due to knowledge of the allocated interventions by outcome assessors. | Low risk of bias: No blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; blinding of outcome assessment ensured, and unlikely that the blinding could have been broken. |
| High risk of bias: No blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding. | |
| Unclear: Insufficient information to permit judgement | |
| Incomplete outcome data Attrition bias due to amount, nature or handling of incomplete outcome data. | Low risk of bias: No missing outcome data; reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size; missing data have been imputed using appropriate methods. |
| High risk of bias: Reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardized difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size; ‘as‐treated’ analysis done with substantial departure of the intervention received from that assigned at randomisation; potentially inappropriate application of simple imputation. | |
| Unclear: Insufficient information to permit judgement | |
| Selective reporting Reporting bias due to selective outcome reporting | Low risk of bias: The study protocol is available and all of the study’s pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way; the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified (convincing text of this nature may be uncommon). |
| High risk of bias: Not all of the study’s pre‐specified primary outcomes have been reported; one or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre‐specified; one or more reported primary outcomes were not pre‐specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; the study report fails to include results for a key outcome that would be expected to have been reported for such a study. | |
| Unclear: Insufficient information to permit judgement |
Appendix 3. Risk of bias assessment tool for cluster randomised studies
| Potential source of bias | Assessment criteria |
| Was recruitment bias adequately prevented? | Low risk of bias: Individuals were not recruited to the trial after the clusters had been randomised. |
| High risk of bias: Individuals were recruited to the trial after the clusters had been randomised (the knowledge of whether each cluster is an ‘intervention’ or ‘control’ cluster could affect the types of participants recruited). | |
| Unclear risk of bias: Insufficient information to permit judgement. | |
| Were baseline imbalances (in terms of either the clusters or the individuals) adequately addressed? | Low risk of bias: The randomised groups were similar at baseline; or the randomised groups were imbalanced at baseline but finally controlled for at the design (such as using stratified or pair matched randomisation of clusters) or analysis stage of the study. |
| High risk of bias: There were baseline imbalances between the randomised groups, but finally they were not controlled for at the design or analysis stage of the study. | |
| Unclear risk of bias: Insufficient information to permit judgement. | |
| Were loss of clusters and participants adequately addressed? | See Appendix 2: "Incomplete outcome data" for criteria of how we will assess this domain. |
| Was the study analysed by correct statistical methods (i.e. taking the clustering into account)? | Low risk of bias: The cluster‐randomised trial was analysed by correct statistical methods, taking the clustering into account. Ways to avoid unit‐of‐analysis errors in cluster‐randomised trials are (see Cochrane Handbook 16.3.3, Higgins 2011b): to conduct the analysis at the same level as the allocation; to conduct the analysis at the level of the individual while accounting for the clustering in the data. Such an analysis might be based on a ‘multilevel model’, a ‘variance components analysis’ or a ‘generalized estimating equations (GEEs)’, among other techniques. |
| High risk of bias: The cluster‐randomised trial was analysed by incorrect statistical methods, not taking the clustering into account. Such analyses tend to create a ‘unit of analysis error’ and produce over‐precise results (the standard error of the estimated intervention effect is too small) and P values that are too small. Although they do not lead to biased estimates of effect, if they remain uncorrected, they will receive too much weight in a meta‐analysis. | |
| Unclear risk of bias: insufficient information to permit judgement. |
Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across one included study.
Risk of bias summary: review authors' judgements about each risk of bias item for one included study.
Comparison 1 Dialysis machine separation vs Usual care, Outcome 1 Incidence of HCV infection: 9 months.
Comparison 1 Dialysis machine separation vs Usual care, Outcome 2 Incidence of HCV infection: 18 months.
| Should patients with HCV be isolated in haemodialysis units for controlling the transmission of HCV? | ||||||
| Patient or population: patients in haemodialysis Intervention: isolation | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect | No. of participants | Quality of the evidence | Comments | |
| Risk with usual care | Risk with isolation | |||||
| Incidence of HCV infection (9 months) | Study population | RR 0.34 | 446 (1) | ⊕⊝⊝⊝ | Very low quality of evidence due to high risk of bias and imprecision | |
| 47 per 1.000 | 16 per 1.000 | |||||
| Incidence of HCV infection (18 months) | Study population | RR 0.22 | 281 (1) | ⊕⊝⊝⊝ | Very low quality of evidence due to high risk of bias and imprecision | |
| 58 per 1.000 | 13 per 1.000 | |||||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). | ||||||
| GRADE Working Group grades of evidence | ||||||
| Outcome or subgroup title | No. of studies | No. of participants | Statistical method | Effect size |
| 1 Incidence of HCV infection: 9 months Show forest plot | 1 | Risk Ratio (M‐H, Random, 95% CI) | Totals not selected | |
| 2 Incidence of HCV infection: 18 months Show forest plot | 1 | Risk Ratio (M‐H, Random, 95% CI) | Totals not selected | |
