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

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.