Table 1. Summary of included studies.

Study	Study type	Outcome adjudicated	Summary
Ninomiya et al.16	Secondary analysis	Stroke (primary outcome) Stroke type (baseline covariate) Cause of death (safety outcome)	Compared outcomes determined by both adjudicators and site investigators to assess whether adjudication had any impact on the results of a single trial.
McArthur et al.17	Simulation study and trial	Functional outcome after stroke (primary outcome)	Simulated scenarios to explore whether increasing mRS reliability translated to increased power. Virtual trial developed that compared mRS scores reported by adjudicators and local site investigators.
López-Cancio et al.18	Secondary analysis	Functional outcome after stroke (primary outcome)	Compared adjudicated and site investigator reported mRS scores in a single trial to determine agreement.
Godolphin et al.3	Secondary analysis and simulation	Stroke type (baseline covariate)	Investigated whether using site investigator reported stroke type gave different results to adjudicated stroke type in a single trial. Increasing error was simulated in the investigator reported outcome to explore scenarios where site investigators were worse at determining stroke type.
Godolphin et al.19	Secondary analysis	Serious adverse events (safety outcome)	Compared serious adverse events determined by site investigators and adjudicators in a single trial.
Easton et al.20	Secondary analysis	Composite including stroke (primary outcome) Cause of death (safety outcome) Major bleeding (safety outcome)	Compared outcomes determined by both adjudicators and site investigators to determine whether adjudication had any impact on the results of a single trial.
Godolphin et al.2	Systematic review and meta-analysis	Stoke (primary outcome) Composite including stroke (primary outcome) Functional outcome after stroke (primary outcome)	Systematic review of 15 trials. Treatment effect using adjudicated outcome compared with treatment effect using site investigator assessed outcome to give an RTE per trial. These RTEs were pooled in a meta-analysis.
Godolphin14	Thesis	Multiple outcomes and outcome types included	Includes Godolphin et al.2, Godolphin et al.19, Godolphin et al.22 and Godolphin et al.23
Farrant et al.21	Secondary analysis	Composite including stroke (primary outcome) Major hemorrhage (safety outcome)	Compared outcomes determined by both adjudicators and site investigators to determine whether adjudication had any impact on the results of a single trial.
Godolphin et al.22	Simulation study	Stoke (primary outcome) Composite including stroke (primary outcome) Functional outcome after stroke (primary outcome)	Simulated systematic error in five trials and random error in simulated trial scenarios. The aim was to identify how much error was required before not adjudicating would change the results of each trial.
Godolphin et al.23	Cost–benefit analysis	Stoke (primary outcome) Composite including stroke (primary outcome)	Estimated the cost of adjudication in nine trials. This was compared with the number of outcomes corrected after adjudication.
Van der Ende et al.24	Secondary analysis	Functional outcome after stroke (primary outcome)	Compared adjudicated and centrally reported mRS scores to determine the impact of adjudication on the results of a single trial.

mRS: modified Rankin Scale; RTE: ratio of treatment effect.