7.2. Critical appraisal of randomized controlled trials for interventions


For the quality appraisal of randomized controlled trials for interventions, the Cochrane Collaboration’s Risk of Bias Tool is recommended [1]. This checklist contains hints on how to interpret and score the individual items, and is summarised in the attachement "Cochrane Collaboration's Risk of Bias Tool". It is also extensively explained in chapter 8 of the Cochrane Handbook (http://www.cochrane-handbook.org/). Each item can be scored with low, unclear or high risk of bias. Importantly, performance bias (blinding) and attrition bias (incomplete outcome data) should be assessed for each critical and important outcome as selected according to GRADE. If insufficient detail is reported of what happened in the study, the judgement will usually be unclear risk of bias.

The recommended level at which to summarize the risk of bias in a study is for an outcome within a study, because some risks of bias may be different for different outcomes. A summary assessment of the risk of bias for an outcome should include all of the entries relevant to that outcome: i.e. both study-level entries, such as allocation sequence concealment, and outcome specific entries, such as blinding.

Some methodological issues, such as the correctness of the statistical analysis, power, etc. are not specifically addressed in this tool, and should be assessed separately.

The scores can be filled in using the template in attachment.


[1] KCE experts initially selected 2 checklists for quality appraisal: the Risk of Bias Tool and the Dutch Cochrane checklist. However, the Dutch Cochrane tool is not used anymore by its authors and was never formally validated.

Cochrane Collaboration's Risk of Bias Tool.doc74.5 KB
Template Risk of Bias tool.doc41.5 KB