Significance of adenosine deaminase in diagnosing tuberculous pleural effusion

Tuberculosis (TB) is a major public health problem in developing countries including Nepal. One of the common presentations of TB is pleural effusion. The diagnosis of tubercular pleural effusion can be difficult because of the low rate of detecting tubercule bacilli by direct stain and culture of pleural fluid for acid-fast bacilli (AFB). Pleural biopsy can be useful but is invasive and requires experts. In this context, pleural fluid Adenosine Deaminase (ADA) level has been proposed as easy, cheap and highly sensitive test for diagnosis of TB pleural effusion. The present study was undertaken to define the role ofpleural fluid ADA value in accurate diagnosis of TB pleural effusion. A Prospective analysis of 100 patients admitted in Nepal Medical College and teaching Hospital with pleural effusion was done. Pleural fluid ADA level was evaluated in all patients, and significance of pleural fluid ADA level in TB pleural effusion was studied. It was found that mean ADA level in pleural fluid was 105.8 +/- 67.23 U/L in cases of TB, as compared to 16.83 +/- 8.91 U/L in malignancy, 44.53 +/- 32.84 U/L in parapneumonic effusion and 15.94 +/- 4.88 U/L in patients with miscellaneous diagnosis. For a cut-off value of 42.19 U/L for diagnosis of TB pleural effusion, sensitivity was found to be 90.8% and specificity 82.8%. Almost all patients diagnosed to have TB pleural effusion responded completely to anti-tubercular treatment. So, we concluded that pleural fluid ADA analysis could be easy, cheap and highly sensitive and specific test for diagnosis of TB pleural effusion.