Performance of the 2017 EULAR/ACR classification criteria in anti-MDA5 associated idiopathic inflammatory myopathy

• Published in: Arthritis & rheumatology (Hoboken, N.J.)
• Main Authors: So, Ho, So, Jacqueline, Lam, Tommy Tsz-On, Wong, Victor Tak-Lung, Ho, Roy, Li, Wai Ling, Mok, Chi Chiu, Lau, Chak Sing, Tam, Lai-Shan
• Format: Journal Article
• Language: English
• Published: United States 25.04.2022
• ISSN: 2326-5205

To evaluate the performance of the 2017 EULAR/ACR classification criteria in a cohort of anti-MDA5 associated IIM patients. Consecutive adult patients with a clinical diagnosis of anti-MDA5 associated IIM from 10 hospitals in Hong Kong were recruited retrospectively. Clinical characteristics were collected by reviewing the electronic medical records. A commercial line-blot immunoassay was used to detect the myositis specific antibodies (MSA). Performance of the 2017 EULAR/ACR classification criteria was examined. Incorporation of the anti-MDA5 antibody in the EULAR/ACR criteria and the MSA-based criteria recently proposed by Casal-Dominguez et al. were also evaluated. Lastly, a new set of phenotypic-serological classification criteria specific for anti-MDA5 was proposed. A hundred and twenty patients with anti-MDA5 associated IIM were recruited. The subgroups were exclusively DM (31.7%) and CADM (68.3%). Eight-six (71.7%) and 49 (40.8%) patients fulfilled the EULAR/ACR classification criteria and the Bohan/Peter criteria respectively. With the addition of Sontheimer's criteria for CADM, 76.7% the patients could be classified by the Bohan and Peter criteria. The sensitivity of the EULAR/ACR criteria could be improved to 98.3% if anti-MDA5 antibody was considered one of the criteria. The criteria by Casal-Dominguez et al. had 100% sensitivity in this cohort. Our newly proposed criteria for "anti-MDA5 syndrome" could also classify 97.5% of the patients. Almost 30% of patients with clinical anti-MDA5 associated IIM could not be classified by the EULAR/ACR criteria. Modification of the existing criteria incorporating anti-MDA5 antibody or development of a new specific set of criteria for "anti-MDA5 syndrome" are suggested.