A retrospective analysis was performed for the data of pleural fluid in inpatients, including 38 cases of tuberculosis, 74 cases of cancer and 108 cases of other diseases. Receiver operating characteristic(ROC) curve was used to determine pleural fluid ADA and LDH optimal thresholds for the diagnosis of tuberculous pleuritis. The clinical diagnosis efficiency was calculated for the diagnosis of tuberculous pleuritis.

ADA activities {median (M) [quartile(Q)]} were 47.30(26.50), 8.15(6.50) and 5.40(8.40)U/L for tuberculosis, cancer and other disease groups, and the differences were statistically significant (Z values were 6.981, 6.978 and 2.302, P<0.05). LDH activities[M(Q)] were 453.68(242.07), 252.00(368.00) and 101.50(192.00)U/L, and the differences were statistically significant (Z=2.419, 5.386 and 4.324, P<0.05). ROC curve showed that the optimal threshold of ADA for the diagnosis of tuberculous pleuritis was 26.7 U/L, the sensitivity was 89.5 %, and the specificity was 89.6%. The optimal threshold of LDH for the diagnosis of tuberculous pleuritis was 173.5 U/L, the sensitivity was 92.1 %, and the specificity was 54.4 %. The sensitivity and specificity of ADA and LDH combination determination were 89.5% and 54.1%.

ADA is an important indicator for tuberculous pleuritis, and LDH has relatively low specificity for the diagnosis of tuberculous pleurtis with certain reference significance. The combination determination has not high clinical diagnosis efficiency.