Adenosine deaminase activity level as a tool for diagnosing tuberculous pleural effusion.

The yield for using a pleural fluid culture to diagnose tuberculous pleural effusion (TPE) is low. Adenosine deaminase activity (ADA) has been shown to have good diagnostic value for TPE. The ADA cutoff point for the diagnosis of TPE is unclear. We attempted to determine the ADA level cutoff point for diagnosing of TPE in Thailand, where tuberculosis is endemic. We reviewed the medical records of patients with newly diagnosed pleural effusion aged >15 years who had a pleural fluid ADAlevel and who underwent a pleural biopsy. The study period was from March 1, 2010 to January 31, 2011. The diagnoses of TPE and malignant pleural effusion (MPE) were based on pathological findings. The diagnostic cutoff level for using ADA to diagnose TPE was determined. Forty-eight patients met study criteria. Of those, 18 patients (37.5%) were diagnosed with TPE. The mean ADA level was significantly higher among patients in the TPE group than in the MPE group (38.2 vs 14.8 U/l, p < 0.001). The cutoff level of 17.5 U/l gave sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 88.9%, 73.3%, 3.33, and 0.15, respectively. An ADA level >17.5 U/l had good diagnostic values among TPE patients in our study.