Background: Functional disability is a major concern for individuals with systemic sclerosis (SSc). The Health Assessment Questionnaire–Disability Index (HAQ-DI) measures the ability to perform activities of daily living, with higher scores indicating poorer function. Objective: To define the frequency and clinical associations of minimum clinically important difference (MCID) change in HAQ-DI scores in SSc. Methods: Australian Scleroderma Cohort Study participants with two or more HAQ-DI scores ⩽ 2 visits apart were included. Generalised estimating equations were used to model the correlates of the MCID improvement (-0.125 points) and MCID worsening (+0.14 points) of HAQ-DI scores. Subgroup analysis in those with incident (⩽5 years SSc duration at recruitment) and diffuse SSc (dcSSc) were performed. Results: Of 1117 participants, 712 (64%) recorded worsening of HAQ-DI scores. Of 827 participants with baseline HAQ-DI ⩾ 0.125 units, 585 (71%) had recorded improvement. Across 3229 study visits, older age (odds ratio (OR) 1.1, 95% confidence interval (CI) 1.1–1.1, p < 0.01), higher skin score (OR 1.1, 95% CI 1.0–1.2, p = 0.01), digital ulcers (OR 1.3, 95% CI 1.0–1.5, p = 0.02), raised C-reactive protein (CRP; OR 1.3, 95% CI 1.1–1.6, p < 0.01) and patient-reported worsening Raynaud’s phenomenon (RP; OR 1.2, 95% CI 1.0–1.4, p = 0.04) and dyspnoea (OR 1.3, 95% CI 1.1–1.6, p < 0.01) were associated with worsening of HAQ-DI scores. In those with incident SSc, raised CRP and patient-reported worsening RP and dyspnoea were associated with worsening of HAQ-DI scores. In dcSSc, only raised CRP was associated with worsening HAQ-DI scores, while in lcSSc higher baseline HAQ-DI score, older age, higher skin score, proximal weakness and worsening dyspnoea were associated with worsening scores. Only higher baseline HAQ-DI score was associated with improvement in HAQ-DI scores in the overall cohort (OR 1.3, 95% CI 1.2–1.5, p < 0.01). Conclusions: Two-thirds of a large SSc cohort demonstrated significant change in physical function. Worsening symptom burden and elevated CRP were important determinants of worsening function.
Fairley et al. (Tue,) studied this question.