Abstract

Background: Tuberculosis (TB) remains a major health problem across the world and most commonly involves the lungs. Diagnosis of TB is based on finding acid-fast bacilli (AFB) in sputum or a positive sputum culture. The sensitivity of sputum smear is only 40-70 and it takes 4-8 weeks for sputum culture results. We decided to measure adenosine deaminase (ADA) activity in bronchoalveolar lavage (BAL) fluid and compare it with sputum and BAL fluid cultures. Materials and Methods: A descriptive study was performed at the Shahid Sadoughi Hospital in Yazd, from 2005 to 2006. Sixty-three patients suspected for pulmonary TB with negative sputum smear for AFB or had other indications for bronchoscopy, were included in the study. Then, fiberoptic bronchoscopy was done and BAL fluid was obtained from all patients. The study patients were divided into three groups as follows: Group 1: patients with positive sputum culture or BAL fluid culture for AFB who were considered as pulmonary TB group. Group 2: patients with negative results for TB, having lung diseases other than TB, (considered as non-tuberculous lung disease group). Group 3: those without pulmonary disease and TB which considered as the control group. Mean ADA levels in BAL fluids were measured in these groups and then compared with each other. Results: Sixty-three patients were enrolled in the study among which 15 cases (mean age:64.06±19.37 yrs) had pulmonary TB, 33 (mean age: 56.18±18.60 yrs) had pulmonary diseases other than TB and 15 cases (mean age: 42.13±21.45 yrs) were considered as controls. Mean ADA level in BAL fluid was 4.13±2.55 IU/L, 2.42±1.06 IU/L and 1.93±0.88 IU/L in TB group, non-tuberculous lung disease group and control group, respectively. This rate was significantly higher in the pulmonary TB group compared to the other two groups (p=0.00). Using Roc curve with a cut-off value of 3.5 IU/L,, the highest sensitivity (57) and specificity (84) were obtained in diagnosis of TB. Conclusion: The results showed that although ADA activity in BAL fluid of pulmonary TB patients was higher than those seen in other diseases, a negative test does not rule out pulmonary TB. Thus, more research is required to find more precise diagnostic methods in this regard. ©2008 NRITLD, National Research Institute of Tuberculosis and Lung Disease, Iran.