Serum urate levels and gout flares: analysis from managed care data

Abstract

Background: The desired serum urate level (SUA) for prevention of gout attacks is widely recommended to be in the subsaturating range, <6.0 mg/dL.

Objectives: The objectives of this study were to evaluate attainment of this target SUA among gout patients on allopurinol in a naturalistic setting and to assess its impact on gout flare risk.

Methods: : This was a retrospective, observational study in a southeastern U.S. managed care organization of approximately 2.2 million members. The first gout claim/prescription within the intake period (January 1, 2000-December 31, 2002) was the index date. Included patients had > or =2 visits with gout International Classification of Diseases, 9th Revision code (274.xx) or > or =1 pharmacy script(s) for allopurinol, colchicine, probenecid, or sulfinpyrazone. Excluded patients were <18 years and/or did not have a 1-year continuous eligibility pre-/postindex date. Gout flares were defined by office/emergency room visit with gout or joint pain code(s) and > or =1 of the following within 7 days of the visit: intraarticular aspiration/injection, joint fluid microscopy, or pharmacy claim for nonsteroidal antiinflammatory drug, colchicine, corticosteroid, or ACTH. Multivariable regression analyses were conducted to evaluate gout flare risk/rate and association with target SUA.

Results: Approximately 40% of 5942 gout patients identified used allopurinol postindex. Among allopurinol users with pre-/postindex SUA data (n = 162), mean SUA was lowered from 8.7 mg/dL to 7.1 mg/dL; reduction was significant (P < 0.001). Among allopurinol users who did not have SUA <6.0 mg/dL preindex (n = 147), only 25% reached target levels during postindex. Despite pharmacotherapy, patients with nontarget levels were 59% more likely to flare than those at target. Allopurinol users who were not at target were 75% more likely to flare.

Conclusion: The failure of allopurinol users to achieve target SUA levels of <6.0 mg/dL may be attributed to lack of awareness of optimal SUA, allopurinol dosing, compliance, and efficacy. Patients who did not achieve target SUA were at increased flare risk.