Diagnostic significance of pleural fluid adenosine deaminase activity in tuberculous pleurisy

Diagnosis of tuberculous pleural effusion (TPE) is difficult because of its non-specific clinical presentation and insufficient efficiency of conventional diagnostic methods. The study was carried out to evaluate the utility of adenosine deaminase (ADA) activity in pleural fluid for the diagnosis of TPE. ADA activity was measured in pleural fluid of 103 pleural effusion patients by colorimetric method using a commercial ADA assay kit. The diagnosis of TPE was made from pleural fluid examinations (including cytology, biochemistry, and bacteriology) and pleural biopsy. Patient with negative result of this methods were diagnosed by response of empirical treatment. Out of 130 cases, 62 (61.1%) had TPE and the remaining 41 (39.8%) had pleural effusion due to non tuberculous diseases. There was statistically significant difference (p < 0.001) between the mean of pleural fluid ADA levels (70.82±22.54 U/L) in TPE group and (30.07±22.93 U/L) in non-TPE group. Of 62 TPE cases, microscopy for AFB and culture for M.tuberculosis in pleural fluid revealed positivity in 9.6% and 22.5% cases respectively, and biopsy of pleura showed typical epithelioid granuloma in only 43.5% cases. The cut-off value of ADA for diagnosing TPE was 40 U/L using a ROC curve, with a sensitivity of 94% and specificity of 88%. Positive and negative predictive value of ADA assay were 92% and 90% respectively. The overall test accuracy was 90%. Pleural fluid ADA assay is therefore a simple, rapid, highly sensitive and specific adjunct test for diagnosis of TPE. DOI: http://dx.doi.org/10.3329/imcj.v5i1.9852 Ibrahim Med. Coll. J. 2011; 5(1): 1-5 Keywords: Pleural fluid; adenosine deaminase; tuberculous pleural effusion