Considerations when planning and conducting large global observational studies: Experience from the DISCOVER study of patients with type 2 diabetes.

DISCOVER is a global programme of observational research that includes patients with type 2 diabetes initiating second-line glucose-lowering therapy from 38 countries worldwide, including many with little or no previous epidemiological data available. More than 15,000 patients were followed-up for 3 years, and comprehensive data were collected using a standardized electronic case report form at enrolment, and 6, 12, 24 and 36 months. The study has formed the basis for a long-term registry that is intended to expand the geographic and clinical scope of the study and allow data collection beyond 3 years. In this review, critical aspects of study planning and implementation are summarized, along with challenges that were faced, to provide a resource for researchers planning similar studies. In particular, it is essential to set realistic expectations regarding the degree of study representativeness that can be achieved, allow for sufficient time to obtain ethics committee approval, develop tools to help recruit patients effectively, ensure that data collection systems are robust, user-friendly and adaptable, plan adequate remote and on-site monitoring, maximize patient retention through continuous engagement with study sites and ensure that everyone involved in the study forms a friendly and effective team. Observational studies such as DISCOVER are crucial for understanding disease epidemiology and management in real-world settings. They are also increasingly used by governmental, regulatory and payor agencies for post-marketing surveillance and when considering new drug submissions. The development of future studies of similar scope and ambition to DISCOVER is encouraged.