Abstract:[Objective] To investigate the diagnostic value of neutrophil extracellular traps (NETs) in peripheral blood for postoperative pneumonia in elderly patients with hip fracture. [Methods] A prospective study was conducted on 57 elderly patients who underwent surgical treatments for hip fracture in our hospitals from January 2019 to February 2022. Based on whether pneumonia developed after surgery, the patients were divided into two groups, and univariate comparison and logistic regression analysis were performed to search the independent risk factor of pneumonia. Furthermore, significance of the risk factors used for predicting postoperative pneumonia was evaluated. [Results] Among the 57 patients, 19 patients (33.3%) were diagnosed with pneumonia, while the remaining 38 patients (66.7%) were of nonpneumonia. Regarding univariate comparison, the pneumonia group was significantly greater than the non-pneumonia group in terms of blood plasma myeloperoxidase-deoxyribonucleic acid (MPO-DNA) that represented NETs [(6.5±2.0) ng/ml vs (3.6±0.7) ng/ml, P<0.05], neutrophil to lymphocyte ratio (NLR) [(6.7±1.9) vs (5.8±0.9), P<0.05] and neutrophil to lymphocyte and platelet ratio (N/LPR) [(6.7±2.0) vs (5.4±0.8), P<0.05], although there were no significant differences in neutrophils, lymphocytes and platelets between the two groups (P> 0.05). As results of logistic regression analysis, the peripheral blood NETs (OR=7.289, 95%CI 1.980~26.836, P<0.05) and N/LPR (OR= 2.087, 95%CI 1.005~4.333, P<0.05) were independent risk factors for postoperative pneumonia. Receiver operating characteristic (ROC) analysis showed that peripheral blood NETs predicted postoperative pneumonia with an area under curve (AUC) of 0.892, optimal cut-off of 4.2, sensitivity of 84.2%, and specificity of 76.3%. Subgroup analysis showed that the incidence of postoperative pneumonia in patients with peripheral blood NETs ≥4.2 was significantly higher than that in NETs content <4.2 group (64.00% vs 9.4%, P<0.05). [Conclusion] The increased content of NETs in peripheral blood is a risk factor for postoperative pneumonia in elderly patients with hip fracture. Monitoring the content of NETs in peripheral blood is significant for the prevention and treatment of postoperative pneumonia in elderly patients with hip fracture.