Using Risk of Bias 2 to assess results from randomised controlled trials: guidance from Cochrane

Ella Flemyng, Theresa HM (Tess) Moore, Isabelle Boutron, Julian P T Higgins, Asbjørn Hróbjartsson, Camilla Hansen Nejstgaard, Kerry Dwan*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

16 Citations (Scopus)
24 Downloads (Pure)


A systematic review identifies, appraises and synthesises all the empirical evidence from studies that meet prespecified eligibility criteria to answer a specific research question. As part of the appraisal, researchers use explicit methods to assess risk of bias in the results’ from included studies that contribute to the review’s findings, to improve our confidence in the review’s conclusions. Randomised controlled trials included in Cochrane Reviews have used a specific risk of bias tool to assess these included studies since 2008. In 2019, a new version of this tool, Risk of Bias 2 (RoB 2), was launched to improve its usability and to reflect current understanding of how the causes of bias can influence study results. Cochrane implemented RoB 2 in a phased approach, with users of the tool informing guidance development. This paper highlights learning for all systematic reviewers (Cochrane and non-Cochrane) from the phased implementation, highlighting differences between the original version of the tool and RoB 2, consideration of reporting systematic review protocols or full review reports that have used RoB 2, and some tips shared by authors during the pilot phase of the implementation.
Original languageEnglish
Article number112102
Pages (from-to)260-266
Number of pages7
JournalBMJ Evidence-Based Medicine
Issue number4
Early online date24 Jan 2023
Publication statusPublished - 21 Jul 2023

Bibliographical note

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© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.


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