Clinical associations of worsening physical function as measured by HAQ-DI scores in systemic sclerosis

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.

To define the frequency and clinical associations of minimum clinically important difference (MCID) change in HAQ-DI scores in SSc.

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.

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).

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.