Does the ACR/EULAR Total Improvement Score Reflect How Individuals With Autoimmune Inflammatory Myopathies Feel and Function?

Abstract

Objective: Little is known as to whether the American College of Rheumatology/European Alliance of Associations for Rheumatology Total Improvement Score (TIS) reflects how patients with autoimmune inflammatory myopathies (AIM) feel and function. We assessed the associations between TIS and changes in the scores of a wide range of patient-reported outcomes (PROs).

Methods: Adult patients with AIM and active disease at baseline who completed a 1-year follow-up visit were identified from a research cohort. PROs included a numerical rating scale for pain, the Functional Assessment of Chronic Illness Therapy - Fatigue (FACIT-Fatigue) scale, the Patient-Reported Outcomes Measurement Information System (PROMIS) Short Form v1.0 Fatigue 8a, the 9-item Patient Health Questionnaire (PHQ-9), and the 36-Item Short Form Health Survey (SF-36) physical and mental component summary scores (PCS and MCS, respectively). Multivariable linear regression models were generated to determine the absolute change in PRO scores for each 20-unit increase in absolute TIS.

Results: We identified 65 patients with active disease for whom TIS could be calculated. At 1 year, 40% showed no improvement, 34% achieved minimal improvement, and 26% achieved moderate improvement. In adjusted models, increase in absolute TIS was associated with statistically significant improvements in pain, PROMIS-Fatigue, FACIT-Fatigue, and SF-36 PCS scores. For FACIT-Fatigue, a significant interaction was identified between age and TIS. In stratified analyses, only patients with shorter disease duration significantly improved in pain and FACIT-Fatigue scores.

Conclusion: The findings of this cohort study support the use of the TIS in AIM research but also highlight potential limitations in its ability to capture outcomes across the broader AIM spectrum, particularly among older individuals and those with longer disease duration.