This paper is to examine the relationship between serum soluble programmed death ligand 1(sPD-L1) levels and the development of interstitial lung disease (ILD) in patients with rheumatoid arthritis (RA).

Serum sPD-L1 were measured by enzyme-linked immunosorbent assay. sPD-L1 levels in RA with ILD, RA without ILD and healthy controls were compared. Associations between ILD and various markers including sPD-L1 and confounding factors were investigated by logistic regression analysis. Diagnostic values of sPD-L1 for the presence of ILD were investigated using receiver operating characteristics curve analysis.

Serum sPD-L1 levels were higher in RA patients with ILD than RA patients without ILD and healthy controls (23.7 ± 9.8 vs. 18.0 ± 7.7 pg/mL, P = 0.01 and 23.7 ± 9.8 vs. 2.9 ± 1.5 pg/mL, P < 0.0001). sPD-L1 levels were positively correlated with RF titer (r = 0.245, P = 0.03), CRP (r = 0.265,P = 0.01), HRCT score (r = 0.265, P = 0.04) and Ferritin (r = 0.442, P = 0.01), but negatively associated with FVC% (r = −0.359, P = 0.01) and DLCO% (r = −0.399, P = 0.008). sPD-L1 and anti-CCP antibody status were independently associated with the presence of ILD during multivariate logistic regression analysis. Sensitivity and specificity of sPD-L1 levels for the detection of ILD in RA patients were 51.7% and 79.3%, respectively (area under the curve = 0.661).

Serum sPD-L1 levels were increased in RA patients with ILD. Increased sPD-L1 levels were associated with the presence of ILD.