Table 1.
The Cochrane Collaboration’s tool for assessing risk of bias
| Bias | Description | Review authors’ judgment |
|---|---|---|
| Random sequence generation (selection bias) | Describe the method used to generate the allocation sequence insufficient detail to allow an assessment of whether it should produce comparable groups. | Was the allocation sequence adequately generated? (Yes/No/Unclear) |
| Allocation concealment (selection bias) | Describe the method used to conceal the allocation sequence in sufficient detail to determine whether intervention allocations could have been foreseen in advance of, or during, enrolment. | Was allocation adequately concealed? (Yes/No/Unclear) |
| Blinding of participants, personnel and outcome. (performance bias and detection bias) | Describe all measures used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. Provide any information relating to whether the intended blinding was effective. | Was knowledge of the allocated intervention adequately prevented during the study? (Yes/No/Unclear) |
| Describe the completeness of outcome data for each main outcome, including attrition and exclusions from the analysis. | ||
| Incomplete outcome data (attrition bias) | State whether attrition and exclusions were reported, the numbers in each intervention group (compared with total randomized participants), reasons for attrition/exclusions where reported, and any re-inclusions in analyses performed by the review authors. | Were incomplete outcome data adequately addressed? (Yes/No/Unclear) |
| Selective reporting (reporting bias) | State how the possibility of selective outcome reporting was examined by the review authors, and what was found. | Are reports of the study free of suggestion of selective outcome reporting? (Yes/No/Unclear) |
| Other sources of bias | State any important concerns about bias not addressed in the other domains in the tool. If particular questions/entries were pre-specified in the review’s protocol, responses should be provided for each question/entry. | Was the study apparently free of other problems that could put it at a high risk of bias? (Yes/No/Unclear) |