Diagnostic performance of Xpert MTB/RIF ultra in detecting Mycobacterium tuberculosis and Rifampicin Resistance in AFB Smear-negative Pulmonary and Extrapulmonary Tuberculosis samples in Malaysia

Abstract

Rapid and highly accurate diagnostic tools are critically needed to diagnose Mycobacterium tuberculosis and rifampicin resistance in AFB smear-negative samples. In this study, we evaluated the diagnostic performance of Xpert MTB/RIF Ultra (Ultra) as a rapid test to diagnose tuberculosis in smear-negative cases in Malaysia. A retrospective study of 1960 smear-negative pulmonary and extrapulmonary samples obtained from patients was conducted. Culture was used as the reference standard for the study. The overall sensitivity and specificity of Ultra on the tested samples were 88.7 % and 77.2 %, respectively, while the PPV was 32.3 % and the NPV was 98.2 %. Ultra showed slightly higher sensitivity in pulmonary (89.9 %) compared to extrapulmonary samples (86.1 %). The overall accuracy of Ultra was 78.5 % (kappa=0.37; 95 %CI: 0.32,0.42). Ultra showed good diagnostic accuracy for detecting MTB and rifampicin resistance in various AFB smear-negative samples. Ultra also had excellent capability in rifampicin resistance detection.