Introducion

Myositis-specific and -associated antibodies (MSA and MAA) may facilitate the diagnosis of inflammatory myopathies (myositis). In subjects with interstitial lung diseases (ILD), they may be the sole clue to such diagnosis. However, the yield of screening all subjects with otherwise idiopathic ILD for MSA and MAA was reported as low. 

Objective

To describe variables associated with positive MSA or MAA among subjects with ILD.

Methods

A retrospective study comprising subjects who were tested with an extended MSA/MAA panel (EUROLINE Autoimmune Inflammatory Myopathies 16 Ag Test) after referal by a rheumatologist or a pulmonologist. We included only subjects whose indication for testing was ILD. Subjects were categorized according to results as "any Ab" (at-least one positive antibody in the assay), "MSA", "MAA" or "no Ab" (no positive results). Patients' characteristics were compared between groups. 

Results

ILD was an indication for testing in 78/152 subjects (51.3%), whose mean age was 65.9-years and 59% were females. MSA were detected in 24, MAA in 23 of ILD patients, and 38 had any positive Ab. While not statisticaly significant, subjects with no Ab were on average older and more often female. Symptoms of myositis (OR=5.1, CI=1.1-25.6), and a positive ANA (OR=4, CI=1.3-12.7) were associated with any Ab positive, while rash was associated with presence of MSA (OR=12.3, CI=1.4-109.7). Groups were comparable in the morphologic patterns of ILD (UIP, NSIP, OP) and respiratory symptoms duration (<1 month, 1-3 months, >3-months).

Conclusions

Clinical characteristics may identify subjects with ILD who will benefit from extended serological testing for MSA and MAA.