A future of data-rich pharmacoepidemiology studies: transitioning to large-scale linked electronic health record + claims data.

Electronic health record (EHR) data are seen as an important source for pharmacoepidemiology studies. In the US health-care system, EHR systems often identify only fragments of patients' health information across the care continuum, including primary care, specialist care, hospitalizations, and pharmacy dispensing. This leads to unobservable information in longitudinal evaluations of medication effects, causing unmeasured confounding, misclassification, and truncated follow-up times. A remedy is to link EHR data with longitudinal health insurance claims data, which record all encounters during a defined enrollment period across all care settings. Here we evaluate EHR and claims data sources in 3 aspects relevant to etiological studies of medical products: data continuity, data granularity, and data chronology. Reflecting on the strengths and limitations of EHR and insurance claims data, it becomes obvious that they complement each other. The combination of both will improve the validity of etiological studies and expand the range of questions that can be answered. As the research community transitions towards a future state with access to large-scale combined EHR + claims data, we outline analytical templates to improve the validity and broaden the scope of pharmacoepidemiology studies in the current environment where EHR data are available only for a subset of patients with claims data. This article is part of a Special Collection on Pharmacoepidemiology.