External Validation and Evaluation of Adding MRI or Extended Myositis Antibody Panel to the 2017 EULAR/ACR Myositis Classification Criteria

Abstract

Objective. To externally validate the European League Against Rheumatism/American College of Rheumatism (EULAR/ACR) classification criteria for idiopathic inflammatory myositis (IIM) and determine the optimal cut points for Australian patients. To determine the level of agreement with traditional criteria and assess the effect of including magnetic resonance imaging (MRI) and an extended myositis antibody panel as well as extending histological criteria to include myofiber invasion. Methods. Data were collected on adult patients referred for muscle biopsy to two Australian teaching hospitals. Patients were scored for "risk of IIM" according to EULAR/ACR criteria, using clinician diagnosis as the gold standard. Results. Overall, 87 of 204 patients had IIM. For patients with muscle biopsy, the optimal cut point of 5.25 (sensitivity 90%, specificity 89%) was lower than the EULAR/ACR cut point of 6.7, which in our cohort showed reduced sensitivity (71% vs 93%) but comparable specificity (89% vs 88%). We found moderate agreement between the EULAR/ACR criteria and Bohan and Peter (κ = 0.45, 95% confidence interval [CI] = 0.28, 0.62, P < 0.001) and Targoff (κ = 0.40, 95% CI = 0.23, 0.57, P < 0.001). Inclusion of MRI (area under curve [AUC] = 0.86, 95% CI = 0.79, 0.93) or non-Jo1 antibodies (AUC = 0.84, 95% CI = 0.77, 0.91) as covariates improved the probability of IIM diagnosis (AUC = 0.80, 95% CI = 0.75, 0.86). Extending histologic criteria to include myofiber invasion slightly improved sensitivity (75% vs 71%) with the same level of specificity (89% vs 89%). Conclusion. Application of the EULAR/ACR criteria to an Australian cohort showed comparable specificity but lower sensitivity, and a lower optimal cut point. Inclusion of MRI or non-Jo1 antibodies as covariates may improve the accuracy of determining the probability of IIM diagnoses. Extending the histologic criteria to include myofiber invasion did not reduce specificity.

External validation of EULAR/ACR classification criteria for idiopathic inflammatory myopathies

“…4 The final complete analysis was presented to an international audience at the October 2018 American College of Rheumatology Annual Scientific meeting 5 and published in ACR Open Rheumatology online in August 2019. 7 We found that in our cohort the EULAR/ACR criteria had very high specificity but lower sensitivity, and lower optimal sensitivity and specificity cut points than that suggested in the EULAR/ACR report. We also explored the effect of MRI and an extended panel of myositis-associated antibodies and MSAs and showed in a logistic regression model that including them as covariates of the EULAR/ACR criteria improved the ability to discriminate between IIM and non-IIM patients.…”

Response to: ‘External validation of EULAR/ACR classification criteria for idiopathic inflammatory myopathies’ by Luuet al

“…Response to: 'External validation of EULAR/ACR classification criteria for idiopathic inflammatory myopathies' by Luu et al We would like to thank Luu et al 1 for their comments on our recent publication in the Annals of the Rheumatic Diseases, entitled 'First external validation of sensitivity and specificity of the European League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for idiopathic inflammatory myopathies with a Japanese cohort'. 2 We are pleased to know similar validation studies of the new criteria [3][4][5][6][7] have been carried out to strengthen our contention. Although Luu et al 1 argue that earlier studies have been published before ours, they were not found with the PubMed search, using the name of the new criteria and validation as keywords, at the time of the submission of our manuscript in April 2019.…”

“…Before our publication, Luu et al gave their presentation in scientific meetings in 2018, 3 4 which was followed by an official publication in the middle of 2019. 5 It is common that presentations at scientific meetings precede the final and formal publication. The meeting abstracts do not appear in the literature databases, reflecting their possible scientific immaturity.…”

The balance between clinical convenience and the new concepts of the 2017 European League Against Rheumatism/American College of Rheumatology classification criteria for adult and juvenile idiopathic inflammatory myopathies

“…While a caveat to the high concordance between the 2017 EULAR/ACR criteria and the Bohan and Peter criteria (95.8% for PM patients and 83.7% for DM patients) demonstrated by Yoo et al [ 7 ] may be that the sample size was too small to represent IIM Korean patients generally, this finding could be of value in clinical research and in the diagnosis of patients in routine clinical practice in Korea. Currently, the focus of attention is on variables such as MSA antibodies and magnetic resonance imaging findings, which have shown promise in the early diagnosis of IIM and in assessing the treatment response [ 11 ]. The development of new classification criteria based on the most up-to-date information, and applicable not only in clinical research but also in clinical practice, is eagerly awaited.…”