Background: Interstitial lung disease (ILD) is one of the main causes of death in patients with rheumatoid arthritis (RA), constituting its early diagnosis a challenge for the clinicians [1]. In this regard, endothelin-1 (ET-1), the most potent endogenous vasoconstrictor, has been described as a profibrotic molecule [2].

Objectives: To explore the role of ET-1 as a biomarker of pulmonary fibrosis in RA-ILD⁺.

Methods: 21 RA-ILD⁺ patients and two comparative groups: 25 RA-ILD^- patients and 21 idiopathic pulmonary fibrosis (IPF) patients were included. Serum levels of ET-1 were determined by ELISA.

Results: RA-ILD⁺ patients showed increased levels of ET-1 compared to those with RA-ILD^- (p<0.01). The ability of serum ET-1 levels to discriminate RA-ILD⁺ patients from those with RA-ILD^- was further confirmed by receiver operating characteristic curves (area under the curve: 0.77, p<0.01). The optimal cutoff value for ET-1 showing the best sensitivity and specificity was 1.02pg/mL. Moreover, RA-ILD⁺ patients presented similar levels of ET-1 than those with IPF. A negative correlation between ET-1 levels and both forced vital capacity and forced expiratory volumen at first second was disclosed in RA-ILD⁺ patients (r=-0.56,p=0.04 and r=-0.65,p=0.01, respectively).

Conclusions: Our study suggests that ET-1 levels are linked to lung injury and worse lung function, supporting its role as a potential blood biomarker of ILD in RA patients.

References: [1]Expert Rev Clin Immunol.2021;17(5):485-497;[2]Am J Respir Cell Mol Biol.2010;42(1):16-20.

Personal funds,VP-C:PI18/00042(ISCIII-ERDF);MSM-G:TRANSVAL22/01(IDIVAL);RL-M: CPII21/00004(ISCIII-ESF).