Gout Assessment Questionnaire: initial results of reliability, validity and responsiveness

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Abstract
We evaluated the psychometric properties of a new gout-specific patient reported outcomes questionnaire. The Gout Assessment Questionnaire (GAQ) and the SF-36 were administered to 126 subjects in a multicenter Phase II program of febuxostat, an investigational treatment for hyperuricemia (serum uric acid >8.0 mg/dl) in patients with chronic gout. The questionnaire was administered at baseline and 1, 6 and 12 months later. The majority of subjects, mean age 54 years, were male, Caucasian and had experienced a gout flare within the last year. Seven domains were identified, all met criteria for reliability and validity. Cronbach's alpha ranged from 0.78 to 0.97. Pearson correlations between GAQ and SF-36 scales were generally low to moderate, with the highest correlation between Gout Pain and Severity and SF-36 Bodily Pain, r = 0.45. Guyatt's statistic (measure of responsiveness) ranged from 0.24 to 1.00 at 12 months. Minimal clinically important differences ranged from 2 (Gout Concern) to 10 points (Productivity). The GAQ has acceptable psychometric properties. Further research is required to confirm results, which may provide more information to improve the GAQ for use in clinical trials.