You are required to assess the methodological quality of the randomized controlled trials you include in your systematic review. Risk of Bias 2 (RoB 2), developed by Cochrane, is the current standard for this assessment.
Why Is RoB 2 Important?
Meta-analysis results produced without a methodological quality assessment may be misleading. Studies prone to bias can systematically produce exaggerated effect sizes.
Since 2022, Cochrane has completed its transition from RoB 1 to RoB 2. The vast majority of current systematic reviews use RoB 2.
The Five Domains of RoB 2
Domain 1: Randomization process
How was the randomization carried out? Was allocation concealment ensured?
Signals: "Computer-generated random sequence" (low risk), only "randomized" written with no detail (some concerns), the same person both randomizing and administering treatment (high risk).
Domain 2: Deviations from the intended intervention
Were participants and healthcare personnel blinded? Were there any deviations from the protocol?
Domain 3: Missing outcome data
How much data is missing? How many of those randomized were analyzed?
Domain 4: Measurement of the outcome
Was the outcome assessment done blinded? Is the measurement method appropriate?
Domain 5: Selection of the reported result
Were all pre-specified outcomes reported? Were only the significant ones published?
Scoring System
There are three outcomes for each domain:
- Low risk of bias
- Some concerns
- High risk of bias
Overall assessment:
- All domains low risk → Overall: Low risk
- High risk in any domain → Overall: High risk
- No high risk but some concerns in some domains → Overall: Some concerns
Applying RoB 2
Robvis package (R): Visualizes the RoB assessment of all studies as a traffic light plot and bar chart. Including it in the article has now become standard.
Official Excel template: Can be downloaded from the Cochrane website; it scores automatically as you respond to the domain questions.
Two independent assessors: The RoB assessment should be performed independently by two researchers. Disagreements are resolved with a third person. Cohen's kappa should be reported.
For support with systematic review quality assessment, request a free consultation.
Where Do People Get Stuck Most in This Analysis?
- In a study, the randomization detail is not written, and you cannot decide whether to assign "some concerns" or "high risk."
- There is too much disagreement between the two assessors, and it cannot be resolved even with a third person.
- You created the traffic light plot, but the reviewers are asking for a rationale of "why did you make this decision."