Factors influencing the effectiveness of allopurinol in achieving and sustaining target serum urate in the national Veterans Administration gout cohort

Abstract

OBJECTIVE: To assess factors associated with the ability to achieve and maintain target serum urate (SU) with allopurinol in patients with gout. METHODS: We used National VA national databases from 2002-2012. Eligible patients had ≥1 inpatient or ≥2 outpatient visits with a diagnostic code for gout, filled a new index allopurinol prescription, had at least one post-treatment SU measured, and met 12-month observability rule. Treatment successes were defined as the achievement of post-index SU <6 mg/dl (success 1) and post-index SU <6 mg/dl that was sustained (success 2). RESULTS: Of the 198,839 unique patients with allopurinol use, 41,153 unique patients (with 47,072 episodes) and 17,402 unique patients (with 18,323 episodes) were eligible for analyses for success 1 and success 2; 42% each achieved (success 1) or achieved and maintained post-index SU <6 mg/dl (success 2). In multivariable-adjusted models, factors associated with significantly higher odds of both outcomes were: older age, normal BMI, Deyo-Charlson index score of 0, rheumatologist as the main provider rather than non-rheumatologist, Midwest U.S. location for the healthcare facility, a lower hospital bed size, military service-connection for medical conditions of 50% or more (a measure of healthcare access priority), longer distance to the nearest VA facility, and lower pre-index SU. CONCLUSION: We identified novel factors associated with maintaining SU <6 mg/dl based on a theoretical model. Several potentially modifiable factors can be targeted by individual/provider/systems interventions for improving successful achievement and maintenance of target SU in patients with gout.