[Expression and clinical significance of CCL18 in bronchoalveolar lavage fluid of connective tissue disease-associated interstitial lung disease].

Objective: To explore the expression and clinical significance of chemokine ligand 18 (CCL18) in Bronchoalveolar Lavage Fluid (BALF) of patients with connective tissue disease-associated interstitial lung disease (CTD-ILD). Methods: From January 2016 to June 2017, BALF of patients with rheumatoid arthritis-associated interstitial lung disease (RA-ILD group), patients with dermatomyositis-associated interstitial lung disease (DM-ILD group), and patients with primary Sjögren syndrome-associated interstitial lung disease (pSS-ILD group) of Peking University People's Hospital were collected. According to the prognosis of each group of patients during hospitalization, they were divided into the discharged and the died. Besides, 30 patients without ILD served as a control group. Levels of CCL18 in BALF of all patients were tested by enzyme linked immunosorbent assay (ELISA). Cells in BALF of RA-ILD group, DM-ILD group and pSS-ILD group were collected and analyzed by absolute different cell counts. Results of high-resolution CT (HRCT) of these three groups were scored. In addition, the area under the curve (AUC) of CCL18 in predicting mortality during hospitalization was calculated. Results: A total of 38 patients with RA-ILD, 54 patients with DM-ILD, and 35 patients with pSS-ILD were enrolled. Levels of CCL18 of those discharged patients of RA-ILD, DM-ILD, and pSS-ILD groups were 8.27(3.62, 14.36), 11.04 (5.86, 17.38), 5.25(2.68, 8.21) µg/L, respectively, which were all significantly higher than that of the control group [2.54(1.26, 3.66) µg/L, all P<0.05]. Furthermore, levels of CCL18 of those deceased patients of RA-ILD and DM-ILD groups were 18.28 (13.82, 22.39), 18.81 (16.29, 22.90) µg/L, which were significantly higher than that of the discharged patients of same group (all P<0.05). Levels of CCL18 were positively correlated with lymphocyte percentage in BALF of RA-ILD, DM-ILD and pSS-ILD groups (r=0.4356, 0.4029, 0.3939, respectively, all P<0.05). Besides, levels of CCL18 were significantly correlated with HRCT scores of RA-ILD and DM-ILD groups (r=0.4242, 0.3319, respectively, both P<0.05). Areas under the curve (AUCs) of CCL18 to predict mortality during hospitalization of RA-ILD and DM-ILD groups were 0.860, 0.851, respectively. Conclusions: Levels of CCL18 are elevated in BALF of CTD-ILD patients, and may be correlated with the severity and prognosis during hospitalization. CCL18 might be served as an indicator of the severity and prognosis of CTD-ILD.