OUTCOME ASSESSMENT FOR CLINICAL-TRIALS - HOW MANY ADJUDICATORS DO WE NEED

Considerable effort is often expended to adjudicate outcomes in clinic al trials, but little has been written on the administration of the ad judication process and its possible impact on study results. As a case study, we describe the function and performance of an adjudication co mmittee in a large randomized trial of two diagnostic approaches to po tentially operable lung cancer. Up to five independent adjudicators in dependently determined two primary outcomes: tumor status at death or at final follow-up and the cause of death. Patients for whom there was any disagreement were discussed in committee until a consensus was ac hieved. We describe the pattern of agreement among the adjudicators an d with the final consensus result. Additionally, we model the adjudica tion process and predict the results if a smaller committee had been u sed. We found that reducing the number of adjudicators from five to tw o or three would probably have changed the consensus outcome in less t han 10% of cases. Correspondingly, the effect on the final study resul ts (comparing primary outcomes in both randomized arms) would have bee n altered very little. Even using a single adjudicator would not have affected the results substantially. About 90 minutes of person-time pe r patient was required for activities directly related to the adjudica tion process, or approximately 6 months of full time work for the enti re study. This level of effort could be substantially reduced by using fewer adjudicators with little impact on the results. Thus, we sugges t that when high observer agreement is demonstrated or anticipated, ad judication committees should consist of no more than three members. Fu rther work is needed to evaluate if smaller committees are adequate to detect small but important treatment effects or if they compromise va lidity when the level of adjudicator agreement is lower. (C) 1997 Else vier Science Inc.