Diagnostic utility of adenosine deaminase in bronchoalveolar lavage (BAL) in pulmonary tuberculosis from a tertiary care hospital in North India

Adenosine Deaminase (ADA) has been acclaimed as a biochemical marker in numerous studies in the diagnosis of tuberculosis of pleura, peritoneum, meninges etc because of its high sensitivity and specificity. As a diagnostic test, ADA offers several advantages; it is rapid, simple, low cost, non-invasive and can be performed easily in most clinical laboratories. The current retrospective study was carried out on a total of 91 specimens of bronchoalveolar lavage collected on bronchoscopy. The samples were collected and sediments were confirmed for presence of tubercular bacilli through Lowenstein Jensen(LJ) media (Gold standard), GeneXpert(CBNAAT).Simultaneously the ADA estimation was done from supernatant fluid obtained after centrifugation of sample.The Mean ADA level for Culture Positive samples in BAL was 5.899± 1.723 and from Culture Negative Samples the Mean ADA was1.217 ± 1.439. The ADA cut off levels of >4.0 IU/L in BAL when compared with LJ culture media (gold standard) showed a sensitivity of 90.0% and a specificity of 97.2%. Upon ROC analysis a high rate of accuracy was recorded in diagnosis of TB through ADA estimation with sensitivity and specificity reaching 100% and 97.2% at a ADA cut off 3.76 IU/L when compared with LJ culture media (gold standard). However, the sensitivity and specificity achieved was slightly lower when ADA results were compared with GeneXpert results.The determination of ADA levels may help in early diagnosis, improve the prognosis and reduce the spread of disease and thereby the test should be included in routine investigations in patients suspected of tuberculosis.