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

BACKGROUND

Increased serum urate (sUA) levels (> or =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 (> or =2 medical claims with ICD-9-CM diagnosis code 274.xx or > or =1 claim with a gout diagnosis and > or =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 > or =1 flare. The number of mean, unadjusted flares increased with sUA. Logistic results showed subjects with baseline sUA > or =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 > or =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.