BACKGROUND Evaluation of pleural effusion is a common medical problem and despite the use of standard pleural fluid measurements and pleural biopsy the aetiology remains uncertain in a considerable number of cases. In our study, we assessed the importance of ADA activity in the diagnosis of pleural effusion. MATERIALS AND METHODS We studied 100 cases of pleural effusions of varying aetiology. Analysis of pleural fluid biochemistry cytology, ADA levels, ZN stain and results of pleural biopsy were analysed. This was a descriptive study. Statistical Analysis-Data were summarised using descriptive statistics such as percentages for categorical variables and mean with standard deviation for quantitative variables. For inferential statistics, two sample t-test was applied. A 'p' value of < 0.05 was considered significant. Sensitivity, specificity, positive predictive value and negative predictive values were calculated for using ADA as a screening test of TB pleural effusion. RESULTS We found Tubercular and Parapneumonic effusions in a younger age group (20-50 yrs.), whereas malignant effusions and those due to cardiac failure were found in an older subset (50-80 yrs.). Pleural biopsy positivity rate was 60%-80% in tuberculosis and 50%-85% in malignant effusions. ZN smear for AFB gave poor yield in sputum and pleural fluid. In all our patients, pleural fluid ADA was above 41.5 U/L with a mean value of 73.92 U/L. CONCLUSION Pleural fluid ADA in tubercular pleural effusion has a sensitivity, specificity, positive predictive value and negative predictive value at a cutoff of 41.5 U/L of 100%, 87%, 90%, 100% respectively.

* where D is vacuous, and S and v are zero. L occupies one top * location of the storage area, the rest of the locations are identi-* fied as being empty. .

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