Background/Purpose: The Health Assessment Questionnaire Disability Index (HAQ) is negatively associated with muscle strength by handgrip test and positively associated with physical performance by timed up and go test (TUG test) in patients with rheumatoid arthritis (RA). Although the HAQ score may improve during treatment of inflammatory arthritis, the association between the self-reported HAQ scores and objective assessments of muscle strength or physical performance over time has not been clearly defined. We therefore aimed to evaluate the association between HAQ and clinical features, muscle strength and directly-assessed physical performance at baseline among patients with RA. Second, we aimed to determine the association between changes over time in self-reported physical function and disease activity, muscle strength, and physical performance.

Methods: In a prospective cohort design, two independent RA cohorts were retrospectively analyzed. Physical function was assessed by HAQ. Disease activity was assessed by the Disease Activity Score in 28 joint (DAS-28-CRP). Pain was assessed by The Visual Analog Scale for Pain (VAS Pain). Muscle strength was assessed by handgrip test and chair test. Physical performance was assessed by TUG test and The Short Physical Performance Battery (SPPB). T test for independent samples, Mann-Whitney U test of independent samples, Pearson’s chi-squared test, Spearman correlation coefficients was performed.

Results: A total of 205 RA patients were studied [North American Cohort (N=115); Brazilian Cohort (N=90)]. At baseline, the mean age was 56.2 ± 10.5 years old in the combined cohort and not statistically different between the two cohorts (p=0.75). The majority of patients were in low disease activity and this was not statistically different between the two cohorts (p=0.92). Brazilian men had greater HAQ than North American men (p< 0.001), while HAQ was not statistically different among women (p=0.15). Brazilian women had lower muscle strength by handgrip test and chair test than North American women (p< 0.05), while Brazilian men showed less muscle strength by chair test than North American men (p< 0.05). In both cohorts the RA patients showed good physical performance. At baseline, HAQ was strongly associated with DAS28-CRP, VAS pain, muscle strength and physical performance (p< 0.05). Patients that experienced a change in HAQ as much as the minimal clinically important difference (0.22) (either improvement or worsening) were not more likely to experience a clinically important change in muscle strength or physical performance over time (p >0.05) in both cohorts. American patients that had a worsening of HAQ over time did show worsening on SPPB (p=0.022).

Conclusion: Poor physical function as measured by HAQ is closely associated with disease activity, pain, muscle strength, and physical performance among patients with RA. However, in this sample, the clinically important changes physical function were not associated with clinically important changes in muscle strength or physical performance over time. These observations highlight a disconnect between changes in self-report of disability over time in patients with RA compared to direct assessments of physical function.

p, values of the difference the American group and Brazilian group. 1 t test for independent samples; 2 Mann-Whitney U test of independent samples. HAQ-DI,by the Health Assessment Questionnaire Disability Index; TUG test, Timed up and go test; SPPB, The Short Physical Performance Battery.

*Spearman correlations; DAS_28–CRP, the Disease Activity Score_28 with C reactive protein; VAS pain, The Visual Analog Scale for Pain; HAQ-DI,by the Health Assessment Questionnaire Disability Index; TUG test, Timed up and go test; SPPB, The Short Physical Performance Battery.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/changes-in-physical-function-were-not-associated-with-clinically-important-changes-in-muscle-strength-or-physical-performance-over-time-a-cohort-study/