The ratio of neutrophil to lymphocyte predicts interstitial lung disease and its prognosis in patients with primary Sjögren’s syndrome: a retrospective analysis

Background: During the course of disease, some patients with primary Sjögren's syndrome (pSS) develop interstitial lung disease (ILD), which leads to a poor prognosis. There is currently a lack of methods to identify high-risk patients with ILD and predict the prognosis. The purpose of this study was to analyze the predictive value of the neutrophil to lymphocyte ratio (NLR) for the occurrence of ILD and its prognosis in patients with pSS.Methods: According to the inclusion and exclusion criteria, patients with pSS admitted to our hospital from May 2009 to November 2020 were included. The patients were divided into either an ILD group or a non-interstitial pneumonia [non-ILD (NILD)] group. We compared the baseline data of the two groups of participants, and the participants were followed up (≥1 year) at clinic visits. Logistic multivariate regression analysis was used to analyze the risk factors related to ILD and prognosis in patients with pSS.Results: A total of 217 patients with pSS were included, of which 71 (32.7%) participants were diagnosed with ILD (ILD group) at the time of pSS diagnosis, and 146 (67.3%) participants had no obvious ILD (NILD group). Based on follow-up results, logistic multivariate analysis revealed that NLR [relative risk (RR) =1.81, 95% confidence interval (CI): 1.15 to 4.73], age (RR =1.43, 95% CI: 1.06 to 3.66), non-regular treatment (RR =1.39, 95% CI: 1.03 to 3.38), ALB <35 g/L (RR =1.32, 95% CI: 1.05 to 3.17), and elevated CRP (RR =1.44, 95% CI: 1.10 to 4.53) were associated with the occurrence of ILD in participants with pSS during follow-up. Age (RR =1.28, 95% CI: 1.06 to 2.25), NLR (RR =1.43, 95% CI: 1.12 to 2.57), non-regular treatment (RR =1.51, 95% CI: 1.18 to 3.01), and ILD (RR =2.05, 95% CI: 1.36 to 4.72) were related to all-cause death during follow-up.Conclusions: The NLR is a risk factor for ILD in patients with pSS. The higher the NLR, the worse the prognosis; ILD significantly increases the risk of death in patients with pSS.