Simple SummaryThis study aimed to assess the diagnostic usefulness of serum receptor for advanced glycation end-products (sRAGE) levels in differentiating between infectious lung diseases and lung cancer. Serum and bronchial washing fluid samples were collected from patients with tuberculosis, pneumonia, or lung cancer, and sRAGE levels were measured using an enzyme-linked immunosorbent assay. The study found that while there was no significant difference in serum sRAGE levels between the groups, bronchial sRAGE levels were significantly different, with lung cancer showing the lowest levels. The results suggest that bronchial sRAGE levels could be used as an auxiliary diagnostic biomarker for lung cancer. The study concludes that bronchial sRAGE has potential as an adjuvant tool for diagnosis in tuberculosis, pneumonia, and lung cancer.AbstractThe receptor for advanced glycation end-products (RAGE) may serve as a diagnostic and prognostic biomarker of lung cancer and lung injury. We explored whether the serum and bronchial levels of soluble RAGE (sRAGE) distinguished infectious lung diseases from lung cancer. We collected serum and bronchial washing fluids (BWFs) from patients diagnosed with pneumonia, tuberculosis, or preoperative lung cancer from April 2016 to March 2022. sRAGE levels were measured using an enzyme-linked immunosorbent assay and we drew receiver operating characteristic (1) curves to determine the cut-off values affording the best diagnostic sensitivities. We enrolled 81 patients including 20 with tuberculosis, 30 with pneumonia, and 31 with lung cancer. Of the 81, 61% were males and the median age was 66 years. The median serum level of sRAGE was 822 (678–1168 pg/mL) and did not differ significantly between the three groups. The median bronchial sRAGE level was 167 (83–529 pg/mL) but 231 (108–649 pg/mL) for tuberculosis, 366 (106–706 pg/mL) for pneumonia, and 103 (32–254 pg/mL) for lung cancer patients (p= 0.018). The ROC curve for the bronchial sRAGE values of lung cancer patients revealed that the optimal cut-off was 118.9 pg/mL. This afforded a sensitivity of 76%, a specificity of 58%, and an area under the ROC curve of 0.695 (p= 0.005). The level of bronchial sRAGE differed significantly between patients with lung cancer and other respiratory diseases; that level may serve as an auxiliary diagnostic biomarker.