Adenosine deaminase, an useful tool for the diagnosis of tuberculous pleuritis in France

Pleural tuberculosis is a diagnosis challenge for usual mycobacterial analysis given that the bacillary concentration is low in the pleural effusion. Adenosine deaminase is a pleural inflammatory marker recommanded for the diagnosis of pleural tuberculosis in the high-prevalence countries. There is not enough data to support its use in a low-prevalence country. Objective: To know the utility of ADA for the diagnosis of pleural tuberclosis in France, a low prevalence country. Material an method: Retrospective study of the exsudative pleural effusion with the ADA dosage (Giusti's method) done in two military hospital near Paris. We compared tuberculous and non-tuberculous pleural effusion. The best cut-off value of ADA for the diagnosis of pleural tuberculosis was found using ROC curves. Results: 183 patients were studied, including 29 tuberculosis, 65 cancers, 5 malignant hemopathies, 32 parapneumonic pleural effusions, 24 purulent pleuritis, 12 old transudative effusions, 14 effusions from others aetiologies. Sixty-eight effusions were rich of lymphocytes including 23 tuberculosis. The young age (≤35 years-old), the foreign origin and the presence of general manifestations were independanltly associated with tuberculosis. The best cut-off value for ADA was 47 UI/l, with Se: 95,7%, Spe: 91,1%, PPV: 84,6%, NPV: 97,6%. When ADA ≥ 70 UI/l, the PPV was 90,5%. Discussion: ADA dosage is usefull in France. Lowers than 47 UI/l, it may exclude tuberculosis. When ADA ≥ 47 UI/l, the result should be interpretated considering the context and the pre-test probability of tuberculosis. When this pre-test probability of tuberculosis is important, ADA ≥ 70 UI/l is very likely for tuberculosis.