Health-related quality of life improvements and response thresholds of myositis outcome measures and response criteria

Abstract

OBJECTIVES: Limited data exist on the clinical associations and responsiveness of myositis core set measures (CSMs) and response criteria using health-related quality of life (HRQoL) assessments like the Short Form Health Survey (SF-36). This study evaluates the associations and improvement thresholds of CSMs and Total Improvement Score (TIS) using SF-36 in idiopathic inflammatory myopathies (IIM). METHODS: Adults with IIM enrolled in two clinical trials and one observational study were assessed. Demographics and myositis CSMs including patient-global assessment (PtGA), physician-global assessment (PhGA), extra global disease activity score (EXGLB), manual muscle testing (MMT-8), Health Assessment Questionnaire (HAQ), creatine kinase (CK), and SF-36 were collected longitudinally. TIS was calculated at 6 months. Spearman's correlation assessed associations between SF-36 domains and summary scores for physical health (PCS) and mental health (MCS) with all CSMs and TIS. A mixed linear model examined longitudinal association. Minimal clinically important difference (MCID) was determined using the anchor method. RESULTS: The study included 105 IIM patients. Most SF-36 domains showed moderate to strong correlations with all CSMs at baseline as well as 6-month changes (delta change), except CK levels at baseline. TIS exhibited significant correlations with delta changes in most SF-36 domains. Longitudinally, significant associations were observed between SF-36 and most CSMs (except MMT-8). Higher thresholds in CSMs and TIS aligned with incremental improvements in PCS. MCIDs for PhGA, PtGA, EXGLB, HAQ, MMT-8 and TIS were 1.1, 1.84, 0.85, 0.65, 3.7, 23.7, respectively. CONCLUSIONS: Most CSMs and TIS in IIM significantly correlated with SF-36 domains, reflecting concurrent HRQoL improvements.