Background MESACUPTM test (enzyme-immunoassay assays; TIF1γ, MDA5, Jo-1, EJ, PL-7, PL-12, and KS; MBL) (MESA) is used for a diagnosis of idiopathic inflammatory myopathies (IIMs) in Japan. On the other hand, EUROLINE myositis Profile 3 (line blot; EUROIMMUN) (EURO) can analyze plural Myositis-specific autoantibodies (MSA: Mi-2, Jo-1, SRP, PL-7, PL-12, EJ, OJ) and Myositis-associated autoantibodies (MAA; Ku, PM-Scl) at the same time, which is used commercially in Western countries. However, the difference between utility of MESA and that of EURO haven't be disclosed.
Objectives To clarify difference between utility of EURO and MESA, and extract the problem of respective examination.
Methods We enrolled 58 patients diagnosed DM/PM in our facility. Polymyositis (PM) and dermatomyositis (DM) were diagnosed according to Bohan and Peter's criteria.1) The MAA and MSA were analyzed using MESA and EURO. In case of MESA (+), MSA (anti-Jo1, anti-PL7, anti-PL12, anti-KS) were identified by specific ELISA. When those results were different, we analyzed by immunoprecipitation. And we analyzed the association between each autoantibody and clinical features.
Results MSA and MAA were detected in 43/58 (74%) (anti-PL7: 12, anti-Jo1: 7, anti-EJ: 3, anti-PL12: 1, anti-OJ: 0, anti-Ro52: 27, anti-PM-Scl75: 7, anti-Ku: 6, anti-PM-Scl100: 1) by EURO. On the other hand, MSA and MAA were detected in 30/58 (52%) (anti-PL7: 9, anti-Jo1: 7, anti-EJ: 4, TIF1γ: 4, MDA5: 3, U1RNP: 3) by MESA. Five patients were MESA (-) and EURO (-). In the case of ARS positive patient, Two of EURO (-) patients was positive in MESA, respectively Jo1 and EJ. Three of MESA (-) patients was positive in EURO. Although MESA(-) and EURO(+) patients had plural MSA and MAA (PL7+Jo1, PL7+PL12, PL7+Ku), MSA and MAA weren't detected by immunoprecipitation in MESA(-) and EURO(+) patients. Two of patients that detected plural MSA or MAA had rapid progressive ILD.
(Association between clinical manifestations and MSA, MAA)
All patients with anti-ARS (anti-Jo-1, anti-PL-7, anti-PL-12 and anti-EJ) had ILD. In addition, anti-ARS were associated with arthritis and mechanic's hands. Anti-Mi-2 positive patients didn't have ILD. Patients detected anti-PM-Scl75, anti-PM-Scl100, anti-Ku were almost overlap syndrome. All of Anti-SRP positive patients was PM.
Conclusions EURO is a convenient and reliable method useful for detection of MSA and MAA. It was suggested the patients whom plural antibodies were detected by EURO have unique clinical course in others.
Bohan, A., Peter, J.B., 1975. Polymyositis and dermatomyositis (second of two parts). N. Engl. J. Med. 292, 403–407.
Disclosure of Interest None declared