ObjectiveTo explore the clinical value of age/pleural fluid adenosine deaminase (age/ADA) ratio and serum lactate dehydrogenase/pleural fluid adenosine deaminase ratio (Cancer Ratio, CR) in the diagnosis of malignant pleural effusions (MPE). MethodsThe study collected 44 patients with MPE and 48 patients with benign pleural effusion (BPE) to compare the differences in age, gender, carcinoembryonic antigen (CEA), age/ADA ratio and CR between the groups. The receiver operating characteristic (ROC) curve of CEA, age/ADA and CR was constructed and the area under the ROC curve (AUC), sensitivity and specificity was calculated to identify the diagnostic performance of the three indicators alone or in combination in MPE. ResultsCEA, age/ADA and CR were significant higher in the MPE group than those in the BPE group (all P<0.05), the AUCs of CEA, age/ADA and CR were 0.768, 0.837 and 0.866, respectively; the sensitivity was 61.36%, 88.64% and 81.82%, the specificity was 85.42%, 75.00%, 83.33%, respectively. The AUCs of CEA combined with age/ADA, CEA combined with CR, age/ADA combined with CR, CEA combined with age/ADA and CR were respectively 0.892, 0.911, 0.837 and 0.907; the sensitivity was 81.82%, 86.36%, 88.64% and 90.91%, the specificity was 79.17%, 79.17%, 75.00% and 77.08%, respectively. ConclusionsAge/ADA and CR demonstrated good diagnostic performance in MPE, moreover, the diagnostic performance can be further improved when combined with the traditional tumor marker CEA, and more research about its diagnostic value is needed in the future.