Abstract Objectives Myositis specific antibodies (MSA) are important in the diagnosis of idiopathic inflammatory myopathies (IIM). In addition, several studies have shown clear utility to stratify IIM patients into more homogeneous subsets based on MSA signatures. However, methods for MSA detection show various degrees of agreement. Here, we aim to compare novel methods for the detection of MSA. Methods MSA were measured in 122 samples using the novel Autoimmune Myopathy reagents employing particle-based multi-analyte technology (PMAT) and compared with ELISA for anti-Mi-2, anti-MDA5, and anti-TIF1-γ antibody detection. Data for line immunoassay was available for 49 samples. Preliminary research thresholds were applied to the assays to calculate MSA prevalence in the sample populations. Results Comparison of PMAT and ELISA for anti-Mi-2, anti-MDA5, and anti-TIF1-γ antibodies revealed high agreement across all three analytes: Kappa agreements between the two methods were 1.00 (95 % CI 1.00–1.00) for anti-Mi-2, 0.89 (95 % CI 0.66–1.00) for anti-MDA5 and 0.84 (95 % CI 0.67–1.00) for anti-TIF1-γ. Quantitative agreements were: Anti-Mi-2 r=0.56 (95 % CI 0.42–0.67), anti-MDA5 r=0.42 (95 % CI 0.25–0.56) and anti-TIF1-γ=0.45 (95 % CI 0.30–0.59). ROC analysis demonstrated excellent discrimination of ELISA positive and negative samples using PMAT, with AUC values of 1.00 for anti-Mi-2, anti-TIF1-γ, and 0.99 for anti-MDA5 antibodies. Conclusions Our data showed high agreement between PMAT and ELISA for three important MSA, providing further evidence of the utility of such methods.
Rimann-Langejuergen et al. (Thu,) studied this question.
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