The challenges of linking health insurer claims with electronic medical records.

This article explores the challenges inherent in linking data from disparate sources-electronic medical records (EMR) and health insurer claims-and the probable benefits of doing so to evaluate several quality measures associated with diabetes. Using the business associate agreement provision of the Health Insurance Portability and Accountability Act, we were able to link health insurer claims with EMR data; however, when restricting the linked data to patients with at least one medication and one diagnosis in the evaluation year, we lost 90 percent of our linked population. Whether this loss was due to difficulties in extracting the data from site EMRs, to changes in insurer coverage over time, or to both was not discernible. Because linking EMR data to health insurer claims can produce a clinically rich longitudinal data set, assessing the completeness and quality of the data is critical to health services research and health-care quality measurements.