The effect of serum urate on gout flares and their associated costs: An administrative claims analysis

BACKGROUND: Increased serum urate (sUA) levels (≥6.0 mg/dL) are associated with increased likelihood of acute gout attacks, or "flares." OBJECTIVES: Identify gout flares with administrative claims data; examine the relationship between sUA and flares; examine the association between sUA and flare-related costs. METHODS: This retrospective administrative claims analysis examined subjects with gout (≥2 medical claims with ICD-9-CM diagnosis code 274.xx or ≥1 claim with a gout diagnosis and ≥1 pharmacy claim for allopurinol, probenecid, colchicine, or sulfinpyrazone) between January 1, 2002 and March 31, 2004. Each subject was observed during 1-year baseline and 1-year follow-up periods. Gout flares were identified with an algorithm using claims for services associated with flares. Outcomes were sUA (mg/dL) and flare-related health care costs. Logistic regression examined the likelihood of flare; generalized linear modeling regression measured the impact of baseline sUA on flare costs, controlling for demographic and health status variables. RESULTS: The study sample comprised 18,243 subjects with mean age of 53.9 years. sUA was available for 4277 (23%) subjects. Sixty-two percent (11,253) of subjects had ≥1 flare. The number of mean, unadjusted flares increased with sUA. Logistic results showed subjects with baseline sUA ≥6.0 relative to sUA <6.0 had 1.3 times the odds of gout flare (P <0.05). Generalized linear modeling results showed that baseline sUA ≥6.0 was associated with 2.1 to 2.2 times higher flare costs than was baseline sUA <6.0 (P <0.05). CONCLUSIONS: sUA was a significant predictor both of gout flare and related costs. This highlights the importance of gout management strategies aimed at controlling sUA.