Diagnostic Performance of Xpert MTB/RIF in Bronchoalveolar Lavage of Sputum-Scarce Recurrent Pulmonary Tuberculosis Cases
Introduction Xpert MTB/RIF has greater sensitivity and specificity than smear microscopy. Bronchoalveolar lavage (BAL) is safe and valuable tool in sputum-scarce and sputum-negative tuberculosis (TB) patients. Our study evaluated the performance of Xpert in BAL specimen of sputum-scarce recurrent TB cases exclusively.
Materials and Methods Sputum-scarce recurrent TB patients who underwent BAL between July 2018 and July 2019 were included. The diagnostic performance of Xpert and acid-fast bacilli (AFB) smear examination in BAL specimen was compared with liquid culture Mycobacterium TB (MTB) and composite reference standard.
Results A total of 126 patients were included in the study. MTB culture was positive in 70 cases and nontuberculous mycobacteria were seen in five cases. Xpert was positive was in 63 patients. Sensitivity of Xpert and AFB smear was 84.29% (95% confidence interval [CI]: 73.62–91.89) and 18.57% (95% CI: 10.28–29.66), respectively, with p < 0.001 proving the superiority of Xpert. Xpert had a specificity of 97.96 (89.15–99.95), positive predictive value of 93.65% (95% CI 85.19–97.42), and negative predictive value of 80.36% (95% CI: 70.26–87.63). Smear had a specificity of 91.84% (95% CI: 80.21–97.58) against 97.96 (89.15–99.95) of Xpert, and smear was positive in nontuberculous mycobacterium cases as well. Xpert showed no cross-reactivity between mycobacterial species. Rifampicin resistance was seen in 8 (12.69%) cases, and 21 patients had other diagnoses.
Conclusion Xpert has greater sensitivity in comparison to AFB smear in BAL specimen. Sputum-scarce recurrent TB cases have a similar chance of rifampicin resistance as sputum smear-positive cases should undergo BAL for Xpert analysis routinely.
Keywordsbronchoalveolar lavage - pulmonary tuberculosis - recurrent tuberculosis - sputum-scarce pulmonary tuberculosis - tuberculosis - Xpert MTB/RIF
03 August 2020 (online)
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