Lee Aymar Ndounga Diakou, Ludovic Trinquart, Asbjørn Hróbjartsson, Caroline Barnes, Amelie Yavchitz, Philippe Ravaud, Isabelle Boutron

Assessment of events by adjudication committees (ACs) is recommended in multicentre randomised controlled trials (RCTs). However, its usefulness has been questioned. The aim of this systematic review was to compare 1) treatment effect estimates of subjective clinical events assessed by onsite assessors versus by AC, and 2) treatment effect estimates according to the blinding status of the onsite assessor as well as the process used to select events to adjudicate. We searched Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, EMBASE, PsycINFO, CINAHL and Google Scholar (25 August 2015 as the last updated search date), using a combination of terms to retrieve RCTs with commonly used terms to describe ACs. We included all reports of RCTs and the published RCTs included in reviews and meta-analyses that reported the same subjective outcome event assessed by both an onsite assessor and an AC. We extracted the odds ratio (OR) from onsite assessment and the corresponding OR from AC assessment and calculated the ratio of the odds ratios (ROR). A ratio of odds ratios < 1 indicated that onsite assessors generated larger effect estimates in favour of the experimental treatment than ACs. Data from 47 RCTs (275,078 patients) were used in the meta-analysis. We excluded 11 RCTs because of incomplete outcome data to calculate the OR for onsite and AC assessments. On average, there was no difference in treatment effect estimates from onsite assessors and AC (combined ROR: 1.00, 95% confidence interval (CI) 0.97 to 1.04; I(2) = 0%, 47 RCTs). The combined ROR was 1.00 (95% CI 0.96 to 1.04; I(2) = 0%, 35 RCTs) when onsite assessors were blinded; 0.76 (95% CI 0.48 to 1.12, I(2) = 0%, two RCTs) when AC assessed events identified independently from unblinded onsite assessors; and 1.11 (95% CI 0.96 to 1.27, I(2) = 0%, 10 RCTs) when AC assessed events identified by unblinded onsite assessors. However, there was a statistically significant interaction between these subgroups (P = 0.03) AUTHORS' CONCLUSIONS: On average, treatment effect estimates for subjective outcome events assessed by onsite assessors did not differ from those assessed by ACs. Results of subgroup analysis showed an interaction according to the blinded status of onsite assessors and the process used to submit data to AC. These results suggest that the use of ACs might be most important when onsite assessors are not blinded and the risk of misclassification is high. Furthermore, research is needed to explore the impact of the different procedures used to select events to adjudicate.