Abstract: Objective To explore the differential diagnostic value of serum PCT, SAA, and ACE2 levels in lung infection during chemotherapy in non-small cell lung cancer (NSCLC) patients. Methods A retrospective analysis was conducted on the clinical data of 80 NSCLC patients who underwent chemotherapy in Wuwei People's Hospital from January 2020 to December 2022 and developed lung infections during the chemotherapy period, as well as 50 NSCLC patients who were not infected during chemotherapy during the same period. They were included in the infected and uninfected groups, respectively. Compare the levels of serum PCT, SAA, and ACE2 in each group, and analyze the differential diagnostic value of individual and combined detection of serum PCT, SAA, and ACE2 in lung bacterial and viral infections in NSCLC chemotherapy patients using receiver operating characteristic (ROC) curves. Results The levels of serum PCT, SAA and ACE2 in infected group were significantly higher than those in non-infected group (P<0.05). The serum PCT, SAA and ACE2 levels of bacterial infection patients were significantly higher than those of the other two types of infection, the serum PCT level of viral infection patients was significantly lower than that of fungal infection patients, the serum SAA level was significantly higher than that of fungal infection patients, and the serum ACE2 level of bacterial infection patients was significantly higher than that of viral infection group (P<0.05). There was no significant difference in serum ACE2 level between viral infection and fungal infection (P>0.05). The AUCs of PCT and SAA were 0.964 (95%CI: 0.926~1.000) and 0.920 (95%CI: 0.856~0.984), respectively, and the cutoff values were ≥47.4 ng/mL and ≥44.9 μg/mL, respectively. The sensitivity and specificity of PCT combined with SAA were 94.74% and 95.24%, respectively. The AUCs of PCT and SAA were 1.000 (95%CI: 1.000~1.000) and 0.965 (95%CI: 0.914~0.984), respectively, and the cutoff values were ≤8.4 ng/mL and ≥16.1 μg/mL, respectively. Conclusion Serum PCT and SAA levels have good differential diagnostic value for lung infection in non-small cell lung cancer patients during chemotherapy, and the combination of the two indicators is more effective.

Key words: PCT, SAA, ACE2, pulmonary infection, non-small cell lung cancer, chemotherapy, differential diagnosis