Screening for Myositis Antibodies in Idiopathic Interstitial Lung Disease

International guidelines recommend screening for connective tissue disease (CTD) with autoantibodies when evaluating patients with idiopathic interstitial lung disease (ILD). Idiopathic inflammatory myositis comprises of a subgroup of CTD diagnosed with myositis antibodies (MA), often presenting with ILD. Our aim was to evaluate the utility of MA screening in patients with idiopathic ILD.

A retrospective analysis was conducted on patients referred with idiopathic ILD to a tertiary centre ILD clinic who were screened for MA. Patients with known or suspected CTD were excluded. Descriptive statistics, univariate analysis and multivariable logistic regression were used to detect associations between MA and patient characteristics.

Of 360 patients, 165 met inclusion criteria and 44 (26.7%) were identified to have MA. Fourteen patients (8.5%) had a change in diagnosis as a result of MA screening. Multivariable logistic regression identified the presence of MA to be associated with current smoking [OR 6.87 (1.65-28.64), p = 0.008] and a diffusing capacity of < 70% predicted [OR 2.55 (1.09-5.97), p = 0.03]. In patients with a change in diagnosis due to MA screening, 3 (1.8%) underwent a surgical lung biopsy and 2 (1.2%) were previously treated with antifibrotic therapy.

Screening for MA in patients with idiopathic ILD can contribute to a change in patient diagnosis, and may prevent invasive testing and unproven use of antifibrotic therapy. These results support the addition of MA to CTD screening panels during the initial evaluation of idiopathic ILD.