Patient-physician discordance in idiopathic inflammatory myopathies: a longitudinal analysis of links to disease activity and damage.

Abstract

Discordance between patient and physician perspectives on disease activity in idiopathic inflammatory myopathies (IIM) can compromise treatment outcomes. This study aimed to characterize patterns of discordance and distinct longitudinal trajectories in the MyoCite IIM cohort. Discordance was defined as a difference between patient (PtGA) and physician (PhGA) global assessments (0-10cm scale) of ≥ ±1cm. Prevalence was assessed at baseline (n = 244) and longitudinally at 6, 12, and 24 months (n = 128). Linear mixed-effects (n = 191) and bidirectional mediation models identified independent drivers and causal pathways. Clinically significant baseline discordance occurred in 19.3% of patients, predominantly manifesting as positive discordance (PtGA>PhGA; 16.8%) across IIM subtypes (dermatomyositis, polymyositis, overlap myositis, anti-synthetase syndrome). Over 24 months, discordance narrowed with treatment. Baseline positive discordance strongly predicted poorer functional capacity (HAQ) at 1 year (p= 0.034). While objective muscle weakness statistically drove the gap (MMT-8: β = -0.013, 95% CI - 0.022 to - 0.004; standardised β = -0.155, p= 0.006), fluctuations had minimal absolute impact. A distinct subset (25%) maintained persistent discordance, exhibiting high subjective pain despite normalized muscle enzymes. Bidirectional mediation analysis revealed discordance unidirectionally drives future functional disability through unmanaged pain (32.1% mediated, p< 0.001) while reverse mediation (HAQ driving discordance via pain) was not statistically significant. Patient-physician discordance in IIM is an active, upstream driver of future functional loss, mediated significantly by pain, rather than a mere reflection of existing objective damage. It serves as a critical marker requiring early targeted pain intervention and integration of patient-reported outcomes into routine clinical monitoring.