ObjectiveTo preliminarily investigate the expression of thymidine kinase 1 (TK1) in serum of patients with lung cancer and patients with acute exacerbation of chronic obstructive pulmonary disease (COPD), and analyze the relationship of TK1 level with gender, age and smoking.MethodsFifty-two patients with lung cancer and 64 patients with acute exacerbation of COPD, who admitted in this hospital from January 2017 to April 2018 and underwent serum TK1 measurement, were retrospectively collected and analyzed. The serum level of TK1 in the patients was detected with immunoblot-enhanced chemiluminescence method.ResultsThe TK1 expression level had no relationship with gender, age or smoking (P>0.05). A total of 14 patients were tested positive for TK1 (TK1 level>2 pmol/L) in the lung cancer patients and the positive expression rate was 26.9%; a total of 23 patients were tested positive for TK1 in the COPD patients and the positive expression rate was 35.9%. The TK1 expression level had a more obvious increase in the patients with acute exacerbation of COPD than that in the patients with lung cancer, but there was no statistical difference between the two groups (U=1 482, P=0.314).ConclusionsThe TK1 expression level is not affected by patient’s gender, age or smoking. The TK1 expression level in patients with acute exacerbation of COPD is higher than that in patients with lung cancer. Abnormal cell proliferation in patients with acute exacerbation of COPD may be stronger than that in patients with lung cancer, but further studies are needed.