VIORICA COJOCARU, ELENA DANTES, MARIANA GABRIELA NOVAC, ALEXANDRA MARIA IONESCU, EDITH SIMONA IANOSI, ELENA RUSU, ROXANA MARIA NEMES THE VALUE OF ADENOSINE DEAMINASE ENZIME LEVEL IN THE POSITIVE DIAGNOSIS OF TUBERCULOUS PLEURAL EFFUSION The etiologic diagnosis of pleural effusion is often difficult, requiring invasive investigations to determine it. In Romania, tuberculosis is a frequent cause of pleural effusion, with the diagnosis of certainty being based on the bacteriological or histopathological examination. Adenosine deaminase (ADA) is an enzyme found in T lymphocytes, stimulated by Mycobacterium tuberculosis, which is why it is considered to be an essential marker of etiologic diagnosis in countries where the TB endemic is elevated. A case-control study was conducted in the Clinical Pneumophthisiology Hospital of Constanta, Romania, in patients diagnosed with tuberculous pleural effusion. The primary endpoint was to establish the cut-off value for ADA in supporting the positive diagnosis of TB pleural effusion, and the secondary objective was to identify the differences between TB pleural effusion and other etiologic types of pleural effusion. A cut-off of 55 UI has a good specificity (80%) and good sensitivity (85%). The study confirms other features of tuberculous pleural effusion as younger age, lower levels of white blood cells and neutrophils, increased number of lymphocytes in pleural fluid, low protein serum level, increased values of pleural lactic dehydrogenase (LDH) and pleural ADA.