Verification and Adjudication of Health Outcomes in Prospective Cohort Studies

The value of prospective biobank studies critically depends on their ability to collect large number of well-characterised disease outcomes on study participants over a prolonged period of time. In contrast with case-control studies which typically collect data on disease cases directly from hospitals, prospective studies collect incident disease outcomes during follow-up over several years or decades by linkage to death or disease registries. Verification of reported disease outcomes in prospective studies is the process of independent validation of the reporting sources for disease outcomes. Adjudication is the process of independent review of all the available evidence on clinical symptoms, signs, imaging, biochemical or histological investigations to classify reported disease outcomes into major disease types and their pathological and/or aetiological sub-types. Hence, disease verification and disease adjudication are complimentary processes to verify the accuracy of reported diagnoses and to classify major diseases into their pathological sub-types. Since most major diseases present as clinical syndromes, reliable classification of disease outcomes is required for studies of genetic and other determinants of such diseases. Verification and adjudication systems require collection of additional information from external sources, including disease registers or medical records from hospitals or primary health care systems for independent review by clinical specialists. The design and implementation of practical procedures needed for disease verification and adjudication in large prospective studies requires feasible and cost-effective systems. Both verification and adjudication systems require regulatory approval to safeguard the confidentiality of personally identifiable data. This chapter discusses the principles and practical procedures required to establish systems for verification and adjudication of disease outcomes in large prospective studies, which will also be of general relevance for other studies.