Sequential value-of-information assessment for prospective drug safety monitoring using claims databases: the comparative safety of prasugrel v. clopidogrel.

Background. Key to conducting active drug safety surveillance using longitudinal health care data is determining whether and when there is sufficient evidence to raise a safety alert. We propose to quantify the expected value of the information (VOI) to be gained through continued monitoring in terms of its potential to reduce health losses among future patients and weigh this against the health cost of exposing current patients during continued monitoring. Objective. To apply this sequential VOI approach to monitoring the comparative safety of prasugrel v. clopidogrel on gastrointestinal (GI) bleeding. Methods. We calculated expected health losses assuming expected mortality, nonfatal myocardial infarction (MI), and nonfatal stroke on clopidogrel were 1.27, 5.93, and 1.14 per 100 person-years, using historical data; relative rates on prasugrel were 0.95, 0.76, and 1.02 based on trial data; and MI, stroke, and GI bleed were 9%, 25%, and 0.1% as bad as death, respectively. We assigned gamma prior distribut...