[Measurement of the functional capacity in rheumatoid polyarthritis: a French adaptation of the Health Assessment Questionnaire (HAQ)].

The ability in performing daily life activities, as assessed with self-administered questionnaire, measures the functional severity of rheumatoid arthritis (RA). The HAQ Disability Index, designed to explore RA, was translated by 3 francophone teams. Three anglophones gave a back-translation. The latters were compared with the original HAQ under the control of 2 bilingual individuals, allowing to the adjustment of the French version. The validity of this measurement tool was studied in a group of recent RA (n = 40, mean disease duration: 2.4 years), longstanding RA (n = 32, mean disease duration: 8.4 years) and controls (n = 59). The construct validity was assessed in a principal component analysis, which showed the contribution of each item of the questionnaire. The intra-subject reproducibility was satisfactory. The HAQ score correlated well with usual clinical and radiological parameters. It differed significantly in the groups, showing a high discriminant ability. A validated instrument for measuring functional ability in French RA patients is now available for the follow-up and therapeutic assessment.