Does the ACR/EULAR Total Improvement Score reflect how individuals with autoimmune inflammatory myopathies feel and function?

Abstract

Little is known as to whether the American College of Rheumatology/European Alliance of Associations for Rheumatology Total Improvement Score (TIS) reflects how patients in the autoimmune inflammatory myopathies (AIM) spectrum feel and function. We assessed the associations between TIS and changes in the scores of a wide range of patient-reported outcomes (PROs). Adult AIM subjects with active disease at baseline visit and a 1-year follow-up were identified from a research cohort. PROs included a numerical rating scale for pain, the Functional Assessment of Chronic Illness Therapy (FACIT)-fatigue, the PROMIS Short Form v1.0-Fatigue 8a, the Patient Health Questionnaire (PHQ-9), and the Medical Outcomes Trust Short Form-36 (SF-36) Physical and Mental Component Summary (PCS/MCS). Multivariable linear regression models were generated to determine the absolute change in PROs for each increase of 20 units in absolute TIS. We identified 65 subjects with active disease for which TIS could be calculated. At year- 1, 40% did not improve, 34% achieved minimal improvement and 26% moderate improvement. In adjusted models, increase in absolute TIS was associated with a statistically significant improvement in pain, PROMIS-fatigue, FACIT-fatigue, and SF-36 PCS. For the 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. The findings from this cohort study support the use of the TIS in AIM research, but also highlight some of its possible limitation in the greater spectrum of AIM especially older individuals and those with longer disease duration.