Utility of GeneXpert MTB/RIF in the Rapid Diagnosis of Extra Pulmonary Tuberculosis

Abstract

Introduction: The diagnosis of extrapulmonary tuberculosis (EPTB) is a challenge. World Health Organization (WHO) recommends the use of GeneXpert MTB/RIF assay [Cepheid, United States of America (USA)], using a heminested real-time polymerase chain reaction (PCR) to amplify a Mycobacterium tuberculosis-specific sequence of the rpoB gene for the rapid and simultaneous detection of M. tb complex (MTBC) and resistance to rifampicin from a clinical specimen. The purpose of this study is to evaluate the performance of the GeneXpert MTB/RIF test with conventional mycobacterial culture in EPTB specimens. Materials and methods: This prospective study (February–October 2017, 11 months) includes data on 287 EPTB specimens that were processed by conventional culture on Lowenstein–Jensen (LJ) medium and the rapid molecular-based GeneXpert MTB/RIF assay system. Results: Among the 287 EPTB samples tested, GeneXpert detected the deoxyribonucleic acid of MTBC in 51 samples (17.8%). Standard bacteriological assays, including acid-fast bacilli microscopy and culture, were positive in 26 (9.1%) and 35 (12.1%) specimens respectively. The performance of GeneXpert results was evaluated against culture as a gold standard. The overall sensitivity and specificity of the Xpert assay were calculated to be 94.6 and 94.4%, respectively. The sensitivity of the Xpert assay with tissue specimens was 84.6 and 80.7% specificity, while there was 86.6% sensitivity and 98.1% specificity with the body fluids. Conclusion: GeneXpert had high performance than culture for the EPTB specimen. It can be a useful tool for the early diagnosis of patients with high clinical suspicion of EPTB. The other major advantage of GeneXpert is that it simultaneously detects rifampicin resistance within 2 hours.

Perception and Risk Factors Associated with Tuberculosis in the Manyara Region, Tanzania

“…Sputa samples were decontaminated using the standard modified Petroff method [16] and mixed with an equal volume of 4% NaOH. The extra-pulmonary samples were not decontaminated, since they are normally sterile [17]. Thereafter both sputa and extrapulmonary samples were centrifuged at 3000× g, the supernatant was discarded, and sediment was re-suspended in 0.8 mL of phosphate buffered saline before inoculation into Mycobacterium Growth Indicator Tube (MGIT).…”