A Prospective clinico-pathological study of fluid cytology and adenosine deaminase levels in pleural effusions

Introduction: The use of biological markers in the diagnosis of tuberculous pleural effusion (TPE) is a breakthrough. Demonstration of elevated levels of Pleural fluid Adenosine deaminase (ADA), interferon-gamma (IFN-γ), tuberculous proteins/antibodies lysozme etc. have been proposed. Adenosine deaminase (ADA) estimation in pleural fluid has been shown as reliable biomarker specially when there is suspicion of tuberculosis. Detection of mycobacterium DNA by PCR is also a proposed test3,4. However India being a developing country with much of its people below poverty line cannot afford expensive tests like ELISA, PCR, IFN-γ. Hence, there is need for relatively cheaper and simple tests with feasibility and sensitivity going hand-in-hand5 TPE being proposed to be a delayed hypersensitive reaction and lymphocytes play a major role in the pathogenesis. With >50% lymphocytes in the pleural fluid, combined criterion of lymphocyte to neutrophil ratio of >0.75 with a raised ADA level increased the specificity of diagnosis in many recent studies10,12. Aims and Objectives: The aims and objectives of our study are - To analyse the cell count, protein and glucose levels in pleural fluid. To correlate cell counts with ADA levels of pleural fluid in order to confirm diagnosis of tuberculosis. To correlate cytomorphology of pleural fluid with clinical and other details available of patient in order to arrive at the diagnosis. Material And methods: The present institutional based prospective study was undertaken after obtaining Ethical clearance. 500 patients presenting with pleural effusion were studied. In all the patients, a detailed history was taken and physical examination of pleural fluid was done in which colour of fluid, amount and nature of fluid was noted. Pleural fluid was received for cytological examination. Total and differential count (TDLC) was done by manual method. Glucose and protein estimation in pleural was also done. Pleural fluid ADA levels wasmeasured by spectrophotometric method. Clinicocytological as well as ADA correlation was done in all cases for the diagnosis of tubercular pleural effusions. All cases except hemothorax and empyema were included in the study. Pleural fluid was collected in 2 separate containers one for biochemical analysis- protein, glucose and ADA estimation, another for TDLC and cytological examination. About 20 cc fluid was collected for the study. The pleural fluid was subjected to the above mentioned tests within 3-4 hours. -Pleural fluid Glucose, Protein, ADA level were estimated by spectrophotometeric method using (COBAS C311, (Hitachi-Roche) instrument.