Objective To investigate the distribution of pathogens causing pulmonary infection after lung cancer chemotherapy and the changes and diagnostic value of serum cytokeratin 19 fragment antigen (CYFRA21-1), high mobility group box 1 protein (HMGB1), and soluble hemoglobin scavenger receptor (sCD163) levels.

Methods A total of 83 lung cancer patients with chemotherapy from July 2022 to November 2023 were divided into non-infected group (n=43) and infected group (n=40) based on their pulmonary infection status, sputum samples were collected from lung cancer chemotherapy patients, and the source of the samples was recorded for bacterial identification.The changes in serum CYFRA21-1, HMGB1 and sCD163 levels were compared between the two groups; a multivariate Logistic regression model was used to analyze the factors influencing pulmonary infection after lung cancer chemotherapy; the diagnostic values of serum CYFRA21-1, HMGB1 and sCD163 levels for pulmonary infection after lung cancer chemotherapy were analyzed.

Results Among the 83 patients with lung cancer chemotherapy, 40 cases had pulmonary infections; a total of 55 strains of pathogens were detected, including 34 Gram-negative bacteria and 18 Gram-positive bacteria, accounting for 61.82% and 32.73% respectively, while only 3 strains of fungi were detected, accounting for 5.45%.Serum levels of CYFRA21-1, HMGB1 and sCD163 in the infected group were significantly higher than those in the non-infected group (P < 0.05).Age, history of lung diseases, CYFRA21-1, HMGB1 and sCD163 were factors influencing pulmonary infection in patients with lung cancer chemotherapy (P < 0.05).The areas under the curve for the diagnostic value of serum CYFRA21-1, sCD163 and HMGB1 levels for pulmonary infection after lung cancer chemotherapy were 0.677, 0.763 and 0.819, respectively (P < 0.05).

Conclusion The main pathogens causing pulmonary infection after lung cancer chemotherapy are Gram-negative bacteria, and the serum levels of CYFRA21-1, HMGB1 and sCD163 increase significantly, which can be used as biological indicators for early diagnosis and assessment of infection.