Abstract: Objective To investigate the expression of serum advanced glycation end products (AGEs) and soluble receptor for AGEs (sRAGEs) in the elderly patients with idiopathic pulmonary fibrosis (IPF) and the correlations with pulmonary function indexes, and to analyze the value of serum AGEs, sRAGEs in the differential diagnosis of IPF, chronic hypersensitivity pneumonitis (cHP) and fibrotic nonspecific interstitial pneumonia (fNSIP). Methods Seventy-nine elderly IPF patients (IPF group), 30 elderly cHP patients (cHP group) and 30 elderly fNSIP patients (fNSIP group) were enrolled in this study from February 2016 to August 2021, while 30 healthy elderly volunteers were enrolled as control group. The levels of serum AGEs, sRAGE, AGEs/sRAGE, pulmonary function indexes such as forced vital capacity predicted (FVC%), percentage of predicted diffusing capacity of lung for carbon monoxide (DLCO%) and total lung capacity (TLC) were detected and compared among the four groups. The diagnostic value of serum AGEs, sRAGE and AGEs/sRAGE were analyzed by receiver operating characteristic (ROC) curve and likelihood ratio test. Pearson correlation coefficient was used to describe the relationship between serum AGEs, sRAGE and pulmonary function in the elderly patients with IPF. Results The levels of FVC%, DLCO% and TLC in cHF group, fNSIP group and IPF group were significantly lower than those in control group (P＜0.05). The level of serum sRAGE in IPF group and CHP group was significantly lower than that in control group and fNSIP group (P＜0.05), and the level of AGEs and the ratio of AGEs/sRAGE were significantly higher than those in control group and fNSIP group (P＜0.05). However, there were no significant differences in serum levels of AGEs and sRAGE between control group and fNSIP group (P＞0.05). ROC curve analysis showed that AGEs, sRAGE, AGEs/sRAGE had good diagnostic value in the differential diagnosis between IPF and fNSIP (all AUC＞0.7). The accuracy and likelihood ratio of AGEs/sRAGE in the differential diagnosis of IPF and fNSIP were higher than those of serum AGEs and sRAGE. Pearson correlation analysis showed that serum AGEs was negatively correlated with sRAGE (r=-0.541, P<0.001), and serum sRAGE was positively correlated with FVC%, DLCO%, TLC (r=0.445,0.452,0.312, all P<0.001), however, AGEs was not correlated to FVC%, DLCO% or TLC (P＞0.05). Conclusions AGEs/sRAGE is helpful for the differential diagnosis of IPF and fNISP, and serum level of sRAGE can reflect the degree of lung function injury in the elderly patients with IPF to a certain extent.

Key words: idiopathic pulmonary fibrosis, chronic hypersensitivity pneumonitis, fibrotic nonspecific interstitial pneumonia, soluble receptor for advanced glycation end products, advanced glycation end products, differential diagnosis