Apply RoB 2 to a specific randomized-trial result, answer each signalling question with the cluster design in view, and write a justification that states how clustering was handled. RoB 2 assesses a result across bias domains using signalling questions and written justifications, producing low risk, some concerns, or high risk judgements (Cochrane Handbook, Chapter 8).
Scope the assessment to one result
Name the outcome, the effect being judged, and the time point before you start. A winter-health trial may report several endpoints, and each result receives its own judgement. Keep the cluster allocation unit and the analysis unit visible in your notes.
Work through the signalling questions
- For the randomization domain, record when clusters were allocated relative to recruitment of participants within them, and whether recruitment timing could have been influenced by knowledge of allocation. State the result of that check in the justification.
- For the confounding domain, identify cluster-level factors that differ between clusters and could affect the outcome, then record whether the design or analysis addressed them. Describe what the trial did and what remains unresolved.
- For the remaining domains, answer each signalling question for the named result and note where the cluster design changes the evidence you would otherwise use.
Write the justification
State the judgement, the signalling questions that drove it, and the specific facts about clustering that informed each answer. Where the trial report leaves recruitment timing or cluster-level confounding unresolved, describe the point as unresolved and name the next verification step, such as checking the trial's protocol or statistical analysis plan.
CONSORT 2025 supports complete reporting of randomized trials; it is a reporting checklist and not a design or quality appraisal tool, so use it to locate reported details and keep RoB 2 as the appraisal framework.