A patient-centred assessment of the 2016 ACR-EULAR Myositis Response Criteria: evaluating the meaningfulness of responses

Abstract

Objectives: The ACR-EULAR Myositis Response Criteria [Total Improvement Score (TIS)] is a composite measure calculated using changes in myositis core set measures. It is unclear if achieving improvement per TIS reflects improvement in any symptoms of patients with myositis. In this study, we examined the association between achieving TIS improvement and patient-centred outcome measures (PCOMs). Methods: Adults with myositis were enrolled in a prospective study with baseline and 6-month visits. Six core set measures were collected at each visit along with the following PCOMs: fatigue [visual analogue scale (VAS) and short form 36 (SF36)], pain (VAS, SF36), health-related quality of life (SF-36), physical function (PROMIS-physical function, SF36, sit-to-stand, timed up-and-go and six-min walk) and physical activity (actigraphy). Mann–Whitney U was used to compare PCOMs between improvement groups. Spearman correlation and regression models were used for correlation and association between TIS and PCOMs, respectively. Results: Of 50 patients (six polymyositis, 24 dermatomyositis, nine necrotizing myopathy, 11 anti-synthetase syndrome) enrolled (mean age: 52, 60% female), 21 patients satisfied the TIS improvement criteria at 6 months. PCOMs including fatigue, pain, quality of life, physical activity and physical function demonstrated significantly greater improvement in patients who had minimal TIS improvement compared with those with no improvement. Greater PCOM improvements were seen with moderate-major TIS improvement. TIS had moderate-strong correlations with most PCOMs. Conclusion: Achieving improvement criteria was accompanied by significant clinical improvements in fatigue, pain, health-related quality of life, physical function, and physical activity. These results support the use of TIS as a clinically meaningful metric of improvement.