Abstract: Objective To explore the value of amylase and pepsin in bronchoalveolar lavage fluid (BALF) in the diagnosis of aspiration pneumonia (AP), and to analyze the etiological characteristics of AP in the elderly patients. Methods A total of 65 subjects admitted to Peking University First Hospital from September 2021 to January 2022 were enrolled and divided into AP group and non-aspiration pneumonia(no-AP) group according to clinical diagnosis. The levels of pepsin and amylase and the pathogenic bacteria in BALF were detected and compared between the two groups. Results There was no significant difference in the level of pepsin between the two groups(P>0.05), but the level of amylase in AP group was significantly higher than that in no-AP group(878.0 IU/L vs 88.6 IU/L, P＜0.001). Receiver operating characteristic (ROC) curve showed that amylase in BALF could predict AP with an area under the curve(AUC) of 0.83. The main pathogens detected in AP group were Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus and Acinetobacter baumannii. The level of amylase of BALF in bacteria-positive patients was significantly higher than that in bacteria-negative patients (408.9 IU/L vs 48.4 IU/L,P＜0.001). Conclusions The level of amylase in BALF helps to timely diagnose AP in the elderly patients.

Key words: aspiration pneumonia, biomarkers, pathogens, pepsin, amylase