Diagnostic value of Endothelin 1 as a marker for diagnosis of pulmonary parenchyma involvement in patients with systemic sclerosis

Background: Systemic sclerosis (SSc) is a connective tissue disease and one of the manifestations associated with this disease is pulmonary involvement. Studies showed that endothelin 1 (ET-1) plays a role in pulmonary dysfunction due to SSc. The aim of this study was to determine the level of ET-1 in SSc patients and to evaluate its association with the early stages of pulmonary fibrosis. Methods: In this cross-sectional study, 48 patients with SSc were enrolled in the study. The stiffness of the skin was evaluated based on the modified Rodnan skin score. CT records, lung function tests and echocardiography were done. The samples were divided into two groups of patients with and without pulmonary parenchymal involvement. Blood sample was taken to measure the serum levels of ET-1 by ELISA method. ANOVA and Tukey HSD tests were used for statistical analysis. Results: According to pulmonary CT scan, 68.2% of patients had pulmonary involvement. There was no significant difference in the presence of honeycomb lesions and fibrosis in lung CT scan of the patients in case of gender (P = 0.819 and P = 0.356, respectively). There was no statistical difference between the results of spirometry in patients with anti-Scl-70 and anti-centromere test. The mean serum level of ET-1 in the studied population was 0.55 ± 0.232 pg/mL, in the men was 0.47 ± 0.14 pg/mL and in the women was 0.55 ± 0.24 pg/mL. There was no significant difference between the two groups in the case of gender and type of the disease (P = 0.475 and P = 0.150, respectively). The ROC diagram of serum level of ET1 in patients based on the type of the disease shows that the serum level of ET-1 of 55% has 50% sensitivity and 52.2% specificity. Conclusion: Serum level of ET-1 could not be used for screening of pulmonary involvement in SSc because its sensitivity and specificity is related to pulmonary fibrosis, honeycomb lesions and disease form. Anti Scl-70 with low levels, DLCO, FVC, FEV1, TLC can be used to assess the possibility of pulmonary involvement and response to treatment.