Concurrent measurement of adenosine deaminase and dipeptidyl peptidase IV activity in the diagnosis of tuberculous pleural effusion

Measurement of pleural fluid adenosine deaminase (ADA) levels aids diagnosing tuberculous pleural effusion (TPE). Dipeptidyl peptidase IV (DPP) enzyme is closely related to ADA. Our aim was to determine the value of concurrent measurement of these T-cell–associated enzymes, ADA and DPP levels in the diagnosis of TPE. Patients with pleural effusion were grouped as TPE, parapneumonic, malignant, congestive heart failure related, and miscellaneous pleural effusions. Pleural and serum ADA and DPP levels were measured. Pleural and serum levels of ADA and pleural DPP were higher in TPE group than the rest. In 7 patients, pleural biopsy revealed granulomatous pleuritis. All of these patients had TPE and had elevated serum and pleural ADA levels. Serum and pleural ADA or DPP levels and pleural ADA and DPP levels correlated with each other. Selecting cutoff values of 40 and 27 IU/L for pleural ADA and DPP, respectively, the sensitivity of concurrent measurement of both enzymes was 77%, specificity 94%, and diagnostic efficiency 91%. ADA and DPP play an important role in tuberculous immunopathogenesis. The utility of DPP in the diagnosis of TPE has never been determined before. Concurrent measurement of ADA–DPP can aid in diagnosing TPE with higher specificity, sensitivity, and efficiency.