The Health Assessment Questionnaire Disability Index is a valid measure of physical function in gout

• Published in: Clinical and experimental rheumatology 2008-07, Vol.26 (4), p.620-626
• Main Authors: TAYLOR, W. J, COLVINE, K, GREGORY, K, COLLIS, J, MCQUEEN, F. M, DALBETH, N
• Format: Article
• Language: English
• Subjects: Activities of Daily Living; Adult; Aged; Biological and medical sciences; Cohort Studies; Disability Evaluation; Diseases of the osteoarticular system; Female; Gout - physiopathology; Humans; Inflammatory joint diseases; Male; Medical sciences; Metabolic diseases; Middle Aged; Miscellaneous. Osteoarticular involvement in other diseases; Other metabolic disorders; Psychometrics; Purines and pyrimidines (gout, hyperuricemia...)
• ISSN: 0392-856X; 1593-098X

There are no disability instruments that have specifically been validated for gout. The aim of this study was to determine the construct validity of the Health Assessment Questionnaire Disability Index (HAQ-DI) in gout and the internal validity using Rasch analysis. An observational cohort study of two groups of clinic patients with gout (n=20, n=53), in which clinical and functional measures were correlated with HAQ-DI scores. Rasch analysis was used to determine the internal validity of summated scores as a measure of physical disability. The HAQ-DI items fitted a Rasch measurement model, confirming internal validity of the scale, although there was evidence of disordered thresholds and rescoring items as a 3-option response rather than a 4-option response improved model fit and resolved the disordered thresholds. HAQ-DI scores showed a bimodal distribution and evidence of floor effects. Clinical indices correlated highly with HAQ-DI scores in gout patients, particularly other measures of physical function. A strong relationship between days of sick leave and HAQ-DI was observed in gout patients (r2=0.44, p