Introduction to the RoB 2 tool for assessing risk of bias in a randomized trial

Session Type
Workshop - training
Target audience
Systematic reviewers and other researchers interested in assessing the validity of a clinical trial
Level of difficulty

Background: Randomized trials provide evidence about the effects of healthcare interventions. However, trial results can be undermined by flaws in design, conduct, analyses and selective reporting. Therefore, assessments of risk of bias in results of the included randomized trials are mandatory in Cochrane systematic reviews. The revised risk of bias tool (RoB 2), published in 2019, is the recommended method for doing this.
Objectives: To explain the key concepts that underpin RoB 2 and gain experience in using it to assess risk of bias in randomized trials.
Description: We will present, implement and discuss the key features of RoB 2: • Specification of the result to be assessed and sources of information used; • Specification of the effect of interest (that of assignment to intervention, or adhering to intervention); • Five consolidated bias domains; • Signalling questions that lead to algorithm-guided risk of bias judgments within bias domains; • Derivation of an overall risk of bias judgment for the assessed result. We will explore the five bias domains included within RoB 2: bias arising from the randomization process, bias due to deviations from intended interventions, bias due to missing outcome data, bias in the measurement of the outcome, and bias in the selection of the reported result. A worked example will be used to provide hands-on training and facilitate discussion. Participants will have the option to complete their assessments in a semi-automated Excel template and are encouraged to bring their own portable device to access detailed guidance that is available at Please note that the facilitators are unable to provide printed copies of the materials.