Evaluating the Diagnostic Yield of Bronchoalveolar Lavage in Suspected Sputum-Negative Pulmonary Tuberculosis

Background: Diagnosing sputum-negative pulmonary tuberculosis (PTB) remains challenging due to low bacillary load and absence of microbiological confirmation. This study evaluated the diagnostic yield of bronchoalveolar lavage (BAL) using Cartridge-Based Nucleic Acid Amplification Test (CBNAAT) and culture in sputum smear-negative, suspected PTB. Methods: This prospective observational study included 50 adults with clinical and radiological suspicion of PTB who tested negative on at least two sputum acid-fast bacilli (AFB) smears and CBNAAT. BAL fluid was analyzed using CBNAAT (GeneXpert MTB/RIF) and mycobacteria growth indicator tube (MGIT) culture. Diagnostic accuracy was calculated using culture as the reference standard. Results were expressed with 95% confidence intervals (CIs). A P -value <0.05 was considered statistically significant. Results: BAL CBNAAT detected Mycobacterium tuberculosis in 26/50 patients (52%), while BAL culture was positive in 12/50 (24%). Ten patients were positive by both modalities. Using culture as the reference standard, CBNAAT demonstrated sensitivity of 83.3% (95% CI: 51.6–97.9) and specificity of 57.9% (95% CI: 40.8–73.7). The positive predictive value was 38.5% and the negative predictive value was 91.7%. Rifampicin resistance was detected in 3/26 (11.5%) CBNAAT-positive cases. Conclusion: Bronchoscopy-guided BAL may be considered in patients with strong clinical suspicion of PTB who remain sputum-negative. It enhances microbiological confirmation and enables early detection of drug resistance.