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Thymidine kinase 1 (TK1) is a tumor biomarker in human malignancies. The purpose of this study was to evaluate the diagnostic efficiency of this marker for lung cancer using the combined analysis of carcinoembryonic antigen (CEA), cytokeratin-19 fragment (CYFRA21-1), neuron specific enolase (NSE) and TK1.From 2013 to 2014, 147 patients with lung cancer and 228 patients with lung benign diseases who were admitted to our hospital were reviewed. Peripheral blood samples were collected for the detection of TK1, CEA, CYFRA21-1 and NSE. The diagnostic value of each marker was analyzed using receiver operating characteristic (ROC) curves and logistic regression equations.The serum levels of TK1, CEA, CYFRA21-1 and NSE were significantly higher than those in patients with lung benign diseases (all P < 0.05). The TK1 concentration was dependent on TNM stage (P = 0.005). The ROC curve analyses showed that the diagnostic value of TK1 combined with CEA, CYFRA21-1 and NSE in lung cancer was significantly higher than that of each biomarker alone (all P < 0.0001). In addition, TK1 combined with CEA, CYFRA21-1, or NSE could also improve the diagnosis of the squamous cell carcinoma, adenocarcinoma and small cell lung cancer subtypes, respectively.The combined detection of TK1 and the other three markers significantly improved the diagnosis of lung cancer. Furthermore, the detection of TK1 combined with that of CYFRA21-1, CEA or NSE increased the diagnostic value of TK1 for lung squamous cell carcinoma, adenocarcinoma and SCLC, respectively.