Evaluate the recently developed particle-based multi-analyte technology (PMAT) assay for the detection of myositis specific antibodies (MSA) in comparison to line immunoblot assay (LIA), multiplex bead assay (MBA), and/or immunoprecipitation (IP).

MSA represent important diagnostic tools for people with inflammatory muscle disease. Variability in testing methods between labs can result in challenges for clinicians interpreting these results. IP remains the gold standard, but other assays offer antigen-specific testing with simplified laboratory methods.

We validated PMAT using samples collected at ARUP Laboratories sent for routine clinical testing using standard testing methods including a combination of IP, LIA, and MBA. Disease controls included sera that were positive by IP, LIA, or MBA for other MSA or myositis-associated antibodies, as well as self-proclaimed healthy donors. Real world clinical validation of the PMAT was done in consecutive samples received at ARUP Laboratories for myositis antibody testing using a combination of IP, LIA, MBA, and/or PMAT. Retrospective analysis of University of Utah antibody-positive patients was performed by chart review by medical doctors to confirm diagnosis.  

We report on the frequency of detection of MSA in a reference laboratory setting, including the agreement between PMAT, IP, LIA, and/or MBA. We also describe the clinical characteristics of University of Utah patients positive for MSA using these methods.

Identification of MSA is important for diagnosis, prognosis, and disease management in people with inflammatory muscle diseases. Combined use of IP and PMAT or LIA improves both sensitivity and specificity for the diagnosis of myositis.