Sensitivity and Specificity of Gene Xpert of Bronchoalveolar Lavage Fluid in the Diagnosis of Sputum Smear Negative Pulmonary Tuberculosis

Background: A substantive number of active pulmonary tuberculosis patients may exhibit negative sputum smear for acid fast bacilli (AFB). Early diagnosis of Pulmonary Tuberculosis (PTB) in this group of patients can reduce tubercular transmission. For the diagnosis of PTB different modalities of investigations like sputum smear and gene X-pert, mycobacterial culture, radiology based investigations like Chest X-ray and CT scan of chest or CT guided fine needle aspiration cytology (FNAC) are there. Study of Gene X-pert on bronchoalveolar lavage(BAL) offer a good option for the early diagnostic challenge of sputum smear negative pulmonary tuberculosis. Objective: To find out diagnostic yields of Gene X-pert on bronchoalveolar lavage in diagnosing Sputum smear negative pulmonary tuberculosis patient. Material and Methods: This intervention based observational, cross-sectional study will be conducted among all the symptomatic and/or radiologically relevant patients who are smear negative but suspected to have pulmonary tuberculosis attending in the department of Respiratory Medicine, Bangladesh Medical University(BMU) within one year after the clearance of IRB. Results: Xpert MTB/ RIF was detected 37.5% cases on BAL fluid. In all cases rifampicin was sensitive. AFB culture on BAL fluid was used as the gold standard. AFB culture was positive 28.57% patients. Considering AFB culture as reference standard sensitivity, specificity, positive predictive Value (PPV), negative predictive value (NPV) of Xpert MTB/RIF on BAL fluid in patients with sputum smear and Xpert negative PTB were 80% (64.6-90.7%), 72.7% (74.8-86.7%) , 61.0% (53.8-75.6%), 91.43% (82.3-95.3%) respectively. Conclusion: Gene X-pert MTB/RIF on broncho-alveolar lavage (BAL) is an useful tool for the diagnosis of smear negative PTB patients. Chest Heart J. 2024; 48(2) : 69-73