Frequency of AFB smear and GeneXpert positivity in bronchoalveolar lavage samples of smear-negative suspected pulmonary tuberculosis patients
DOI:
https://doi.org/10.61529/idjp.v35i1.483Abstract
Background: Pulmonary tuberculosis (TB) patients with negative sputum smears is a daunting task. Bronchoalveolar lavage (BAL) can get lower respiratory samples for analysis. We evaluated the frequency of AFB smear and GeneXpert positivity on BAL samples of smear-negative suspected pulmonary TB.
Material and methods: This cross-sectional study conducted at the Department of Pulmonology, Ojha Institute of Chest Disease, Karachi, Pakistan from July 2025 to Nov 2025. Patients aged 20 to 70 years, either gender, suspected of having pulmonary TB and negative for AFB on at least three consecutive sputum smear samples were included. All patients underwent bronchoscopy and BAL. BAL fluid was tested for Mycobacterium TB using both AFB smear microscopy and the GeneXpert MTB/RIF assay.
Results: Out of 150 patients, BAL AFB smear was positive in 62 (41.3%; 95% CI: 33.5–49.2), while GeneXpert detected M. tuberculosis in 100 (66.7%; 95% CI: 59.1–74.2). AFB smear positivity was higher in rural than urban patients (56% vs 34%, p=0.010), whereas GeneXpert positivity was higher among unemployed compared to employed patients (75.6% vs 56.9%, p=0.015).
Conclusion: Bronchoscopy with BAL significantly improved the diagnostic yield in sputum smear-negative presumptive TB patients. GeneXpert testing on BAL fluid identified a significantly more TB cases than smear microscopy, thus emphasizing its role for rapid, confirmatory diagnosis.
Keywords: AFB smear, Bronchoalveolar lavage, GeneXpert positivity, Pulmonary tuberculosis, Respiratory disease
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