Abstract Objectives To develop and validate enzyme-linked immunosorbent assay (ELISA) systems for the detection of autoantibodies against signal recognition particle (SRP), nuclear matrix protein 2 (NXP2), and small ubiquitin-like modifier activating enzyme (SAE). Methods Serum samples from 288 individuals were analysed, including 183 patients with idiopathic inflammatory myopathies (IIM), 20 with other neuromuscular diseases, 35 with non-IIM systemic autoimmune rheumatic diseases, and 50 healthy controls. ELISA systems were established using recombinant SRP, NXP2, and SAE proteins expressed in insect cells or Escherichia coli. The diagnostic performance of the ELISAs was assessed in comparison with the ‘gold-standard’ immunoprecipitation (IP) assays. Results The ELISAs demonstrated high concordance with IP assays, with positive and negative percent agreements of 97.4% and 100% for anti-SRP, 100% and 99.6% for anti-NXP2, and 100% and 99.6% for anti-SAE antibodies, respectively. Conclusions The newly developed ELISA systems showed excellent agreement with IP assays, supporting their applicability for routine clinical use in detecting anti-SRP, anti-NXP2, and anti-SAE autoantibodies.
Murakami et al. (Mon,) studied this question.