Human epididymis protein 4 as a new diagnostic biomarker for rheumatoid arthritis-associated interstitial lung disease

This study aimed to evaluate the role of human epididymis protein 4 (HE4) in the diagnosis and determination of the severity of interstitial lung disease (ILD) in rheumatoid arthritis (RA) patients.HE4 levels in peripheral blood (PB) and bronchoalveolar lavage fluid (BALF) samples were determined via electrochemiluminescence immunoassays in 102 RA patients (46 patients with ILD and 56 patients without ILD) and 51 healthy controls (HCs).Serum HE4 levels were significantly higher in RA-ILD patients (141.8±65.92 pmol/l) than those in the RA-no ILD patients (82.67±26.17 pmol/l) and healthy controls (35.72±7.6 pmol/l) (p0.0001). Consistent with serum HE4 levels, BALF HE4 levels were significantly higher in RA-ILD patients (637.6±154.9 pmol/l) than those in the RA-no ILD patients (427.3±111.2 pmol/l) and healthy controls (206.9±30.46 pmol/l) (p0.0001). In RA-ILD patients, HE4 levels were positively correlated with HRCT (high-resolution computed tomography) fibrosis scores, whereas a significant inverse relationship was found between HE4 levels and lung function parameters (such as, diffusion capacity of the lung for carbon monoxide (DLCO)). The logistic regression analysis showed that high levels of BALF HE4 (≥595 pmol/l) were associated with RA-ILD (odds ratio [OR] =8.09; 95% confidence interval [CI] =1.317-49.682; p=0.024).Serum and BALF HE4 levels were elevated in RA-ILD patients and strongly associated with the severity of ILD, thus supporting their potential clinical value as a new diagnostic aid for patients with RA-ILD.