Adenosine Deaminase (ADA) is a very useful parameter for the differential diagnosis of Tuberculosis pleural effusion and malignant pleural effusion, specifically with a higher incidence of tuberculosis. It is an enzyme abundantly present in T-lymphocytes and it is widely distributed in human tissues, with the highest activities found in T-Lymphocytes, Monocytes and Macrophages . It has great clinical utility as a marker for cellular immunity and cell-mediated hypersensitive reactions. ADA exists in two isoforms as ADA1/ADA2.