Comparison of Three Immunoassays for the Detection of Myositis Specific Antibodies

Abstract

Objectives: Standardization of myositis specific antibody (MSA) detection is of high importance because these antibodies are relevant for diagnosis and stratification of patients with idiopathic inflammatory myositis (IIM) and have the potential to be used in classification criteria. Many laboratories rely on immunoprecipitation (IP) for the detection of MSA but this approach is compromised by logistic, standardization, and regulatory challenges. Therefore, reliable alternatives to IP are mandatory. Here we aimed to compare three methods for the detection of MSA. Methods: Our study initiated from a cohort of 1,619 IIM patients (BIRD/University of Bath serology service and UKMyoNet cohorts) and resulted in 157 unique serum samples enriched for higher prevalence of MSA characterized by the laboratory's routine methods, IP and line immunoassay (LIA: Euroimmun). All samples were tested using a novel fully automated particle-based multi-analyte technology (PMAT, Inova Diagnostics, research use only). Analyses included antibodies to PL-7, PL-12, SRP, NXP2, Mi-2, SAE, EJ, MDA5, TIF1γ, SRP, NXP2. Results: Overall high agreements were observed between novel methods (LIA and PMAT) and IP (Cohen's kappa 0.46–0.96) for the detection of MSA. Lowest level of agreement was found for EJ and highest for SAE. Conclusion: The data hold promise for advancements in standardization of MSA assays as well as for the potential inclusion of MSA in future classification criteria.

Efficacy and Tolerability of Nintedanib in Idiopathic-Inflammatory-Myopathy-Related Interstitial Lung Disease: A Pilot Study

“…Responsible pathogens were recognized based on repeated cultures/smears of bronchoalveolar lavage fluid (BALF) or sputum before related treatment. To acquire the positivity of 12 myositis-specific antibodies (MSAs, anti-MDA5, anti-TIF1γ, anti-Jo-1, anti-OJ, anti-PL-7, anti-PL-12, anti-EJ, anti-Mi-2α, anti-Mi-2β, anti-NXP2, anti-SRP and anti-SAE1) and 4 myositits-associated antibodies (MAAs, anti-Ro-52, anti-PM-Scl75, anti-PM-Scl100, anti-Ku) of IIM patients ( 34 ), sera from these patients were acquired at their first outpatient visit or within the first week of admission. The samples were tested using the EUROLINE Autoimmune Inflammatory Myopathies 16 Ag (IgG) commercial line blot assay (Euroimmun, Lübeck, Germany) encompassing a membrane strip with the 16 autoantigens in light of the manufacturer's instructions.…”

Correspondence on ‘Standardisation of myositis-specific antibodies: where are we today?’

“…Considering the controversial data between Espinosa-Ortega’s1 and Cavazzana’s7 8 studies, it is emblematic that there is still no concordance among LIA and IP even for anti-Jo1, the most common MSA and the first discovered in this group of diseases. The low agreement of IP versus other methods, evidenced by recent studies,2 6 7 9 raises the question of whether IP should still be considered the reference method for detecting MSA.…”

“…Another study that has opened Pandora’s box is Vulsteke’s10 which compared three different DIA/LIA assays showing significant differences in diagnostic performance which, however, varied according to the MSA considered. This great variability clearly demonstrates the urgent need to harmonise methods, and that their clinical validation against the reference IP method remains an issue 8 9. In addition, studies conducted so far are retrospective, including patients diagnosed using previous criteria,11 and mostly performed on cohorts in which there was a very small number of some MSA, representing a further bias for comparative analysis 12 13.…”

Understanding and managing anti-MDA 5 dermatomyositis, including potential COVID-19 mimicry

“…1 ). No restrictions were applied based on the age or method of detection of the anti-MDA5 antibody [ 13 ]. After an initial screening of titles and abstracts, relevant articles were retained.…”