ADA levels are usually ascended in inflammatory effusions, such as pleural, pericardial and articular effusions caused by bacterial infection and granulomatous inflammation, as well as malignant tumors and autoimmune diseases.[16,17] Though the AUC of pleural fluid, ADA was slightly larger compared with age/ADA (Z = 0.346, P = 0.7297, Fig. 1A, B), the PLR of age/ADA was 36.69 and was considerably higher than that of pleural fluid ADA. This evidence concerns the gene ADA and cancer.