Linking physician characteristics and medicare claims data: issues in data availability, quality, and measurement.

BACKGROUND: Increasingly, investigators are using administrative databases to answer research questions requiring physician characteristics information. This article provides a roadmap for investigators who use Medicare data to answer such questions, focusing on use of the Surveillance, Epidemiology, and End Results (SEER)-Medicare files.
METHODS: Three data sources that can be linked to identify physician characteristics-Medicare claims, the Unique Physician Identification Number (UPIN) Registry, and the American Medical Association (AMA) Masterfile-were examined for data availability, linkage rates, and quality. These databases also were used to explore measurement issues regarding physician specialty and practice volume.
RESULTS: Over 98 percent of UPINs identified from the Medicare claims could be linked with both the AMA Masterfile and the UPIN Registry. The AMA Masterfile is the best source of sociodemographic and medical training information; the Medicare claims are the best source of practice ZIP code; and the UPIN Registry is the best source of practice organization data. The operationalization of variables such as physician specialty and practice volume is dependent on the specific research question that is being addressed.
CONCLUSION: Administrative databases, such as SEER-Medicare data linked to AMA Masterfile or UPIN Registry data, are an important resource for investigators interested in assessing the relationship between physicians' personal and practice characteristics and the content or outcomes of clinical care.