Relationship between physician specialty and allopurinol prescribing patterns: a study of patients with gout in managed care settings.

OBJECTIVE: Allopurinol is used to lower serum uric acid (sUA) levels in gout patients. The objective of this study was to investigate the influence of physician specialty on allopurinol treatment patterns and sUA control. DESIGN AND METHODS: This was a retrospective study using claims from a managed care database of US health plan enrollees. Gout patients at least 18 years of age who received allopurinol were identified from the database between January 1, 2002 and April 30, 2007. The index date was defined as the date of the earliest allopurinol claim, and patients were required to have health plan enrollment for at least 365 days prior to and following the index date for inclusion. Physician specialty was determined using the index allopurinol claim. Dosage of allopurinol prescription(s) and number of gout flares were determined from claims data. sUA measurements were used to assess goal attainment over a period of at least one year following the index allopurinol prescription. RESULTS: There were 3363 patients with gout of whom 69.9% received an index allopurinol prescription from a generalist/internist, 5.7% from a rheumatologist, 2.6% from a nephrologist, and 21.8% from a physician with other specialty. Of patients receiving their index prescription from a nephrologist, 38.7% reached the sUA goal of <6 mg/dL (357 µmol/L), as compared to patients prescribed by a rheumatologist, generalist/internist, or other physician (35.4%, 31.4%, and 39.4%, respectively; P = 0.015). When controlling for patient characteristics, multivariate analysis did not reveal statistically significant different odds of sUA goal attainment based on prescribing physician specialty, though separate analyses indicated that patients prescribed by a nephrologist had fewer gout flares. Change in allopurinol dosage from initial to final dose was more frequent among patients prescribed by rheumatologists and nephrologists. CONCLUSION: There is significant heterogeneity in the specialists' management of sUA levels in patients with gout, possibly reflecting differences in case mix and treatment approaches. Limitations related to the use of claims data, such as inability to observe medications filled over-the-counter, should be considered when interpreting study results.