Translation, internal consistency, reliability and validity of the Thai version of Gout Assessment Questionnaire version 2.0 (GAQ 2.0)

Abstract

Objectives: To translate the Gout Assessment Questionnaire version 2.0 (GAQ2.0) with Gout Impact (GI) Scale (GIS) into Thai and determine its psychometric property in gout patients with acute arthritis (acute arthritis group) and during the intercritical period (chronic gout group). Methods: Translation followed the ISPOR recommendations. Cronbach’s α, intraclass correlation coefficient (ICC) and standardized response mean (SRM) were used to determine internal consistency, reliability and responsiveness to change, respectively. Correlations between GI subscales with generic health-related quality of life (HRQoL) questionnaires (SF-36, HAQ-DI and EQ-5D-5L) and gout clinical parameters were determined. Results: The acute arthritis group and the chronic gout group comprised 27 and 92 patients, respectively. Internal consistency was sufficient for all GI subscales (Cronbach’s α = 0.80–0.98), reliability was moderate to good in most GI subscales (ICC = 0.54–0.88) and responsiveness to change was moderate to large in most GI subscales (SRM = 0.43–0.98). The GI subscales correlated better with SF-36 than HAQ-DI and EQ-5D-5L. In the acute arthritis group, the unmet gout treatment needs subscale showed large and moderate negative correlation with tophi and serum uric acid, respectively. In the chronic gout group, the gout concern overall subscale had statistically significant, moderate correlation with overall gout severity rated by the patients and number of gout attacks over the past year, while the well-being during attack subscale and total GIS score had statistically significant, moderate correlation with overall gout severity rated by the patients. Conclusion: The Thai GAQ2.0 GIS showed acceptable internal consistency, reliability and responsiveness to change and correlated significantly with generic HRQoL questionnaires and clinical parameters.