Validation of 2017 classification criteria for adult and juvenile idiopathic inflammatory myopathies proposed by EULAR/ACR in Chinese patients

Objectives To evaluate the ability of 2017 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIM) to classify IIM in comparison with the 1975 Bohan and Peter criteria in Chinese patients. Methods Two hundred and twenty-one inpatients with suspected IIM (including 40 children) were retrospectively included in this study. The performance of the 2017 EULAR/ACR criteria was evaluated by sensitivity, specificity, positive predictive value, negative predictive value and classification rate, in comparison to the 1975 criteria, with clinical diagnosis as the gold standard. Results The sensitivity, specificity, positive predictive value, negative predictive value of the 2017 EULAR/ACR criteria in IIM classification were 92.7%, 87.0%, 90.1% and 90.4%, respectively, in contrast to the 1975 Bohan and Peter criteria of 84.0%, 52.2%, 61.8%, and 77.9%. The classification rate of the 2017 criteria was also much better than that of the 1975 criteria (90.2% vs 67.4%). The performance of the new criteria in general, as well as the new criteria with muscle biopsy was better. Most IIM patients were correctly further sub-classified by the classification tree. The positive rate of myogenic lesions in electromyography, muscular inflammatory edema in magnetic resonance imaging and specific antibodies of myositis were significantly higher in the IIM group than those in the control group (P < 0.001, all). Conclusions The 2017 EULAR/ACR criteria exhibited high sensitivity, specificity, classification rate in the Chinese IIM patients, which was superior to the 1975 criteria. The new criteria showed potential as clinical classification criteria in the future.