Assessing risk of bias in a randomized trial

Julian P T Higgins, Jelena Savović, Matthew Page, Roy Elbers, Jonathan A C Sterne

Research output: Chapter in Book/Report/Conference proceedingChapter (Book)Otherpeer-review


Key Points: This chapter details version 2 of the Cochrane risk-of-bias tool for randomized trials (RoB 2), the recommended tool for use in Cochrane Reviews. RoB 2 is structured into a fixed set of domains of bias, focusing on different aspects of trial design, conduct and reporting. Each assessment using the RoB 2 tool focuses on a specific result from a randomized trial. Within each domain, a series of questions (‘signalling questions’) aim to elicit information about features of the trial that are relevant to risk of bias. A judgement about the risk of bias arising from each domain is proposed by an algorithm, based on answers to the signalling questions. Judgements can be ‘Low’, or ‘High’ risk of bias, or can express ‘Some concerns’. Answers to signalling questions and judgements about risk of bias should be supported by written justifications. The overall risk of bias for the result is the least favourable assessment across the domains of bias. Both the proposed domain-level and overall risk-of-bias judgements can be overridden by the review authors, with justification.
Original languageEnglish
Title of host publicationCochrane Handbook for Systematic Reviews of Interventions
EditorsJulian P. T. Higgins, James Thomas, Jacqueline Chandler, Miranda Cumpston, Tianjing Li, Matthew J. Page, Vivian A. Welch
Place of PublicationChichester UK
Number of pages24
ISBN (Electronic)9781119536659
ISBN (Print)9781119536628, 9781119536611
Publication statusPublished - Sep 2019

Cite this

Higgins, J. P. T., Savović, J., Page, M., Elbers, R., & Sterne, J. A. C. (2019). Assessing risk of bias in a randomized trial. In J. P. T. Higgins, J. Thomas, J. Chandler, M. Cumpston, T. Li, M. J. Page, & V. A. Welch (Eds.), Cochrane Handbook for Systematic Reviews of Interventions (2nd ed., pp. 205-228). Wiley-Blackwell.