Comparison Studies of GENXPERT versus MGIT Culture of Bronchial Lavage in Sputum Smear Negative Suspected Pulmonary Tuberculosis

摘要

Introduction: Xpert MTB/RIF (Cepheid, USA) is an automated real-time PCR system that simultaneously detects TB and resistance to rifampicin. The test has excellent accuracy when performed on sputum and is endorsed by the World Health Organisation (WHO) and the USA Federal Drug Administration. Aims: To measure the diagnostic yield of bronchoalveolar lavage gene Xpert and compare it with traditional mycobacterial cultures in smear-negative and sputum-scarce pulmonary tuberculosis. Methods: A prospective observational study at a tertiary care hospital in India was conducted. A total of 200 patients who were 18 years or older under evaluation for clinico‐radiological features of PTB with a history of a cough >2 weeks and a chest X‐ray with pulmonary parenchymal involvement were recruited after ensuring two consecutive sputum negative smears or inability to produce adequate sputum. A volume of one ml of BAL sample was used to detect mycobacterium tuberculosis by the G4 version of Xpert? MTB/RIF (Cepheid, USA) and by traditional mycobacterial cultures. cartridges without initial decontamination or centrifugation. Sensitivity, specificity and predictive values were calculated with 95% class intervals (CIs). McNemar’s test was used for comparison of sensitivities. Result: The results showed that the AFB smear test had 76.83% (95% CI: 66.20-85.44) sensitivity, 100.0% (95% CI: 96.92-100.0) specificity with 100.% PPV and 86.13% (95%CI: 80.72-90.21) NPV compared to culture report. The Gene Xpert test had better sensitivity 84.15% (95% CI: 74.42-91.28) and good specificity 97.52% (95% CI: 92.75-99.47) with 97.52% (95% CI: 92.75-99.47) PPV and 89.84% (95% CI: 84.30-93.58) NPV compared to AFB smear test. The Gene Xpert test to detect resistance against culture report had 89.47% (95% CI: 66.86-98.70) sensitivity, 90.61% (95% CI: 85.39-94.43) specificity with 50.0% (95% CI: 38.27-61.73) PPV and 98.90% (95% CI: 95.67-99.67) NPV. Conclusion: Xpert MTB/RIF has high sensitivity and specificity for diagnosis of both smear positive and smear negative PTB cases with high rates of detection of RIF resistance and greater concordance with gene sequencing for RIF resistance when com- pared with culture.