Biomarkers of interstitial lung disease associated with primary Sjogren's syndrome.

OBJECTIVES: The aim of this study was to investigate serum biomarkers linked to primary Sjogren's syndrome (pSS)-associated interstitial lung disease (ILD). METHODS: 69 pSS patients were consecutively enrolled and evaluated via quantitative ILD scoring based on high-resolution computed tomography (HRCT). Biomarkers of interest were assessed by multiplex enzyme-linked immunosorbent assays (ELISAs). RESULTS: Among consecutively enrolled patients with pSS, the presence of pSS-ILD was 50% based on the presence of radiographically defined interstitial lung abnormalities (ILA) meeting specified criteria for mild/moderate (ILA 2) or severe (ILA 3) disease. Age, immunoglobulin M (IgM), C-reactive protein (CRP), and serum levels of eotaxin/CCL11, Krebs von den Lungen-6 (KL-6), TNFalpha, and TGFalpha were significantly higher in the combined pSS-ILD group (ILA 2 + ILA 3) than in the pSS-no-ILD and pSS-indeterminate ILD groups (ILA 0 and ILA 1, respectively) in unadjusted analyses (p < 0.05 for all variables). A binary logistic regression model revealed that disease duration and KL-6 levels were associated with the presence of pSS-ILD (p < 0.05). Complementary least absolute shrinkage and selection operator (LASSO) modeling showed that age, KL-6, and TNF-alpha effectively differentiated pSS-ILD (ILA 2 + ILA3) from pSS without ILD (ILA 0 + ILA 1), with an area under the curve (AUC) of 0.883 (p value < 0.0001). CONCLUSIONS: Patient age, disease duration, and serum levels of both KL-6 and TNFalpha were the most discriminating factors associated with the presence of ILD in our pSS patients. Higher levels of CRP, IgM, eotaxin, TGFalpha, and TNFalpha should also prompt the search for occult as well as clinically evident lung involvement based on statistically significant univariate associations with pSS-ILD. CLINICAL TRIAL REGISTRATION: None.