1175: Inclusion of All Myositis Specific Autoantibodies or Other Rashes Leads to Better Sensitivity but Lower Specificity of 2017 EULAR/ACR Myositis Classification Criteria for Dermatomyositis

Yusra Hasan¹, Katharine Ching Chung², Dana Ascherman³, Siamak Moghadam-Kia⁴, Chester V. Oddis³ and Rohit Aggarwal³, ¹CHI Health Creighton University Medical Center, Omaha, NE, ²University of Pittsburgh Medical Center, Mckeesport, PA, ³University of Pittsburgh, Pittsburgh, PA, ⁴University of Pittsburgh Medical Center, Pittsburgh, PA

Background/Purpose: Idiopathic Inflammatory Myopathies (IIM), collectively known as myositis, are heterogeneous disorders characterized by muscle weakness and muscle inflammation. ACR/EULAR classification criterion for IIM was published in 2016 that showed the sensitivity and specificity for probable diagnosis 87%/82% without biopsies, and 93%/88% with biopsies. The criteria is currently being used in most clinical trials and research studies. However, it has been criticized for its lack of a full panel of autoantibodies as well as the non-inclusion of other Dermatomyositis-specific rashes. The aim of our study was to evaluate if the addition of other myositis-specific antibodies (MSAs) and/or DM rashes other than Gottron papules/sign or heliotrope rash would improve the accuracy of the criteria.

Methods: Data were obtained from a prospectively collected myositis registry at a single tertiary care center but retrospectively extracted in subjects with an initial visit between 1995 to 2020. The classification criteria dataset included all variables of 2017 EULAR/ACR as well as Bohan and Peter myositis classification criteria.Additional variables were verified by chart review if/when required and all variables and scores were cross-checked by 2 physicians. Classification scores were re-calculated by adding:

1. all non-Jo1 MSA/MAA receiving the same score as Jo-1,
2. all other DM rashes except Gottron papule/sign, and heliotrope (i.e., shawl sign, V-neck, holster sign, malar rash not sparing nasolabial fold, mechanics hands, periorbital edema) receiving the same score as Gottron papules.
3. both a & b.

Psychometric properties of the 2017 EULAR/ACR classification criteria and proposed modifications were calculated using the diagnosis made by expert rheumatologist physicians as the gold standard.

Results: 798 patients with IIM including 268 with dermatomyositis, 41 with clinically amyopathic dermatomyositis (CADM). In our analysis, 2017 EULAR/ACR showed 91% accuracy, with high sensitivity (87% and 73%) and specificity (94%, and 93%), with and without muscle biopsy, respectively. Bohan and Peter showed lower sensitivity and specificity of 57% and 74% respectively.

The modification of adding other MSA/MAA along with Anti Jo1 leads to a minor improvement in sensitivity (88% and 77% with and without biopsy respectively) without loss of specificity. Adding other DM rashes with Gottron papules increases sensitivity significantly (96% and 79% with and without biopsy, respectively) but with a decrease in specificity (86%). (Table 1)

The modification of adding other MSA/MAA as well as other DM rashes together improves sensitivity the best but at the cost of specificity.

Conclusion: The addition of other skin rashes and/or MSA to the 2016 EULAR/ACR criteria improves sensitivity but at a cost of specificity. Modification of the EULAR/ACR classification criteria is required to overcome some of the shortcomings of the current criteria.




Y. Hasan: None; K. Chung: None; D. Ascherman: None; S. Moghadam-Kia: None; C. V. Oddis: Boehringer-Ingelheim, 5, Cabaletta, 5, EMD Serono, 5, Novartis, 5, Pfizer, 1; R. Aggarwal: Actigraph, 2, Alexion, 2, ANI Pharmaceuticals, 2, Argenx, 2, AstraZeneca, 2, Boehringer-Ingelheim, 2, 5, Bristol-Myers Squibb(BMS), 2, 5, CabalettaBio, 2, Capella Bioscience, 2, Corbus, 2, CSL Behring, 2, EMD Serono, 2, 5, Galapagos, 2, Horizon Therapeutics, 2, I-Cell, 2, Janssen, 2, 5, Kezar, 2, Kyverna, 2, Mallinckrodt, 5, Merck, 2, Octapharma, 2, Pfizer, 2, 5, Q32, 5, Roivant, 2, Sanofi, 2, Teva, 2.