Positioning of myositis-specific and associated autoantibody (MSA/MAA) testing in disease criteria and routine diagnostic work-up

Nowadays, the importance of detection of myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) in diagnosis and in delineating disease subsets of idiopathic inflammatory myopathy (IIM) is highly acknowledged by IIM experts. Consequently, MSA/MAA are increasingly integrated in expert-based myositis (sub)classification criteria as well as in routine diagnostics. In contrast, MSA/MAA are under-represented in data-based (sub)classification criteria, mostly related to the lack of sufficient data on the wide spectrum of MSA/MAA in large multicenter cohorts. Unfortunately, the current commercially available assays to detect MSA/MAA show variable analytical and clinical performance characteristics. This challenges the design of prospective multicenter studies on MSA/MAA as well as the optimization of their routine clinical use. Additional validation studies and continuous harmonization initiatives on MSA/MAA detection from the pre-analytical to the post-analytical phase (e.g. from defining request criteria to guidelines for reporting), will be needed to overcome these hurdles. To speed up this process, we encourage close collaborations between IIM clinical experts, laboratory professionals and diagnostic companies.

Automated summary

The importance of detecting myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) in the diagnosis and classification of idiopathic inflammatory myopathy (IIM) is widely acknowledged by experts. However, the lack of sufficient data on MSA/MAA in large cohorts has hindered their inclusion in data-based classification criteria. In addition, commercially available assays for detecting MSA/MAA show variable performance characteristics, which poses challenges for future studies and routine clinical use. Collaboration between clinical experts, laboratory professionals, and diagnostic companies is encouraged to overcome these hurdles.