Combined use of the polymerase chain reaction and detection of adenosine deaminase activity on pleural fluid improves the rate of diagnosis of pleural tuberculosis

Study objectives: Evaluation of the combined use of polymerase chain reaction (PCR) and adenosine deaminase (ADA) activity on the diagnosis of pleural tuberculosis (pTB) in a region of high prevalence of tuberculosis. Patients: PCR and determination of ADA activity were performed on the pleural fluid of every patient presenting with pleural effusion suspected to be associated with tuberculosis. The case definition of pTB involved parameters including the combination of clinical and radiologic findings; biochemical, microbiologic, and cytologic examination of the pleural fluid; and the histopathologic findings of pleural fragments obtained by biopsy. The diagnosis of pTB was confirmed in any patient presenting with positive culture findings of Mycobacterium tuberculosis, either on the pleural fluid or other biological material, or the presence of histopathologic findings suggestive of pTB on pleural biopsy, and also, in the absence of negative laboratory results, those patients with clinical improvement after empirical treatment. Results: We studied 45 patients with pleural effusion. Of these, 16 patients met the diagnosis of pTB by our broad case definition. PCR findings were positive in six patients. The reaction was also positive in a patient whose diagnosis of tuberculosis could not be confirmed. ADA activity was considered positive in 11 patients with pTB. The combined use of PCR and ADA activity confirmed pTB in 14 patients; however, when analyzed in combination with the conventional methods, diagnosis of pTB was achieved in all 16 patients. Conclusion: Our results show that, even in a highly endemic area, neither PCR nor ADA activity should be relied on as a single test that substitutes for the diagnostic methods already available, but rather they should be used as an extra tool in the diagnosis of pTB. The combined analysis of PCR and ADA activity, however, is a very useful diagnostic approach to achieve a more rapid and precise diagnosis in the cases of pTB.