Reported disability in relation to observed activity limitation, grip strength and physical function in women and men with rheumatoid arthritis

BACKGROUND: The self-reported Health Assessment Questionnaire (HAQ) is specifically designed to assess disability in arthritic patients. In many studies women report higher functional disability than men. The reasons for this difference are suggested to be multifactorial. We therefore evaluated functional disability assessed by HAQ in women and men with rheumatoid arthritis (RA) in relation to observed disability, grip force and physical function. METHODS: Patients with RA, 51 women and 49 men, completed the HAQ on three occasions, some weeks apart. Between HAQ1 and HAQ2, all patients performed 17 of the 20 activities (7 domains) included in the HAQ under observation in a specially designed environment, the observed HAQ. During the same day, grip force, measured by GRIPPIT and physical function assessed by the SOFI (Signals of Functional Impairment) index were evaluated. Differences between groups were studied by the chi-square test, Mann-Whitney U test and Wilcoxon Sign Rank test. Correlations were analysed by Spearman rank correlation. Comparisons between repeated measures were performed using Friedman’s test. RESULTS: Median (IQR) total HAQ1 score was 0.50 (0.88) for women and 0.25 (0.84) for men, p = 0.038, and the observed HAQ score (7 domains) 0.57 (0.9) for women and 0.43 (0.96) for men, p = 0.292. The correlations between reported HAQ1 score (7 domains) and observed HAQ score were strong, r = 0.860, p < 0.001 in women, and r = 0.820, p < 0.001 in men. For some activities the patients, both women and men, reported lower difficulty than that observed. Women had lower grip force than men, median (IQR), right and left 126 (84) Newton, versus 238 (146), p < 0.001, and there was a negative correlation between grip force and most of the separate activities in HAQ in both genders. SOFI index was similar in women and men, median (IQR) 0 (3.0) versus 0 (2.0), p = 0.277, with a moderate correlation to HAQ. CONCLUSIONS: The results indicate that in well-treated patients with RA the correlations between reported and observed HAQ scores were strong, similarly in women and men. We found no evidence that the patient’s opinion was dependent on unawareness of her/his own ability. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s41927-021-00184-5.