Long-term therapy for chronic gout results in clinically important improvements in the health-related quality of life: short form-36 is responsive to change in chronic gout

Abstract

Short Form-36 (SF-36) is a validated outcome measure to assess health-related quality of life (HRQOL) in patients with gout. We assessed responsiveness to change of SF-36 in patients with gout. SF-36 was administered at baseline and at yearly intervals. We assessed the minimal clinically important differences (MCIDs) at the first and second year. We also assessed the responsiveness to change (effect size) and interpreted it based on Cohen's criteria. We modelled the improvement (defined as ≥MCID) in SF-36 scales and summary scores. Covariates included age, presence of tophi, comorbidities, baseline joint involvement, baseline serum urate, change in serum urate and the number of flares from baseline to 12 months. Of 99 subjects, 96 were male, mean age was 57.1 years, disease duration was 8.2 years and 40.4% had tophi. Ninety-two patients were treated with urate-lowering therapy (ULT) and daily colchicine, and seven were only on colchicine. Baseline mean serum urate level was 8.9 mg/dl and mean number of flares was 4.7 over last year. ULTs were associated with reduction in serum uric acid and number of flares (P < 0.001 for both) over 12 months. Therapy was associated with 22-70% of the patients achieving MCID in SF-36 scores at 12 months. Effect size estimates ranged from negligible to large (SF-36 mental component summary 0.08-bodily pain 1.09). Reduction in flares independently predicted improvements in three SF-36 physical scales (P = 0.001-0.06). Improvement in SF-36 scores was maintained at 2 years. In our real-life observational cohort, chronic urate lowering therapy and colchicine was associated with clinically meaningful improvements in HRQOL at 1 year and then maintained at 2 years. SF-36, especially physical domains and physical component summary, are responsive to change in gout.