Diagnostic yield of bronchoalveolar lavage GeneXpert in smear-negative and sputum-scarce pulmonary tuberculosis

Background
Tuberculosis remains a common public health hazard in the underdeveloped world. Initial approach to diagnosis is sputum smear staining for acid-fast bacilli, however only 40% of patients are smear positive.


Aim and objectives
To assess the diagnostic yield of GeneXpert in bronchoalveolar lavage in a smear negative or sputum scarce suspected case of pulmonary tuberculosis.


Methods
This analytical cross-sectional study included 50 patients who had clinical and radiological signs consistent with pulmonary tuberculosis and three negative Ziehl–Neelsen sputum smears or unobtainable sputum. All patients underwent fiberoptic bronchoscopy guided bronchoalveolar lavage that was sent for evaluation with GeneXpert and mycobacterial culture (Löwenstein–Jensen). Sensitivity analysis was carried out using culture as the gold standard.


Results
There is a statistically significant increase of positive TB cases diagnosed by bronchoalveolar lavage GeneXpert, as all cases were positive (100%) including 17 patients that were sputum scant, while all cases diagnosed by smear acid-fast bacilli were negative (100%) (P<0.05) However, there is statistically insignificant difference of positive TB cases diagnosed by bronchoalveolar lavage GeneXpert (100%) and bronchoalveolar lavage L.J culture (100%) (P>0.05).


Conclusion
Bronchoalveolar lavage GeneXpert has superior diagnostic yield than acid-fast bacilli smear microscopy, and the yield is as effective as mycobacterial cultures, but much faster and time saving. It can be used as a gold standard for TB diagnosis.