Clinical contribution of myositis-related antibodies detected by immunoblot to idiopathic inflammatory myositis: A one-year retrospective study

• Published in: Autoimmunity (Chur, Switzerland) Vol. 51; no. 2; pp. 89 - 95
• Main Authors: Lecouffe-Desprets, Marie, Hémont, Caroline, Néel, Antoine, Toquet, Claire, Masseau, Agathe, Hamidou, Mohamed, Josien, Regis, Martin, Jérôme C.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 17.02.2018; Taylor & Francis Group
• Subjects: Idiopathic inflammatory myositis; immunoblot; Immunology; Life Sciences; muscle biopsy; myositis-associated antibodies; myositis-related antibodies; myositis-specific antibodies; Idiopathic inflammatory myositis; myositis-associated antibodies; muscle biopsy; myositis-specific antibodies; immunoblot; myositis-related antibodies; Team4; CRTI; Team1
• ISSN: 0891-6934; 1607-842X
• DOI: 10.1080/08916934.2018.1441830

In this study, we aimed at evaluating the contribution of an extended myositis-related antibodies (Abs) determination by immunoblot to the diagnosis, classification, and prognosis of idiopathic inflammatory myositis (IIM). Medical records of all the patients (n = 237) with myositis-related Ab requests addressed to our department over a one-year period were retrospectively analyzed. Patients were classified as IIM, auto-immune disease (AID) other than IIM, and other diagnosis, and examined for their Ab profiles as determined by immunoblot. Ab positivity was qualified semi-quantitatively as low or strong according to the manufacturer's recommendations. Among the 45 Ab-positive patients, 49% were diagnosed an IIM, 22% another AID, and 29% another diagnosis. The clinico-serological patterns of the myositis-related Ab + patients fully recapitulated those described in the literature. Among non-IIM patients, anti-PM-Scl was the most frequently detected Ab (38%), followed by anti-Mi-2 (15%), and anti-OJ (12%). Importantly, strong Ab positivity was significantly more detected in IIM vs. non-IIM patients (82% vs. 35%; p = .002). This difference was further increased when comparing MSAs only (95% vs. 36%; p = .0004). Accordingly, strong Ab positivity associated with high specificity (96%) and positive likelihood ratio (pLR =12) for IIM. Our data suggest that while myositis-related Ab, including MSA, can be detected by immunoblot in non-IIM patients, strong positivity is nevertheless highly predictive of IIM. In conclusion, this work suggests that relevant clinical contribution to IIM is provided by the immunoblot determination of myositis-related Ab, more especially when considering strong positive detection of MSA.