ABSTRACT

The advances in diagnostic research to detect pulmonary tuberculosis have resulted in the development of a real time Polymerase Chain Reaction (PCR) assay on the gene Xpert platform that simultaneously detects rifampicin resistance, integrates sample processing and greatly simplifies testing. This is done by amplifying M. tuberculosis complex-specific region of the rpob gene which is probed with molecular beacons to detect the presence of rifampicin resistance-determining mutations. In this study, 100 (21.3%) MTB/RIF positive samples out of 470 samples from patients with presumptive TB were considered to have tuberculosis. Out of the 470 samples, 74 samples were randomly picked and cultured. Cultures of 22 patients yielded Mycobactrial growth, 17(77.3%) of the isolates were identified as M. tuberculosis complex and 5(22.7%) were Nontuberculous mycobacteria (NTM). Comparing Smear microscopy with MTB/RIF assay, it was determined that the performance of MTB/RIF assay for rapid diagnosis of pulmonary tuberculosis was higher than that of smear microscopy. MTB/RIF assay showed a detection rate of 21.3% while smear microscopy showed a detection rate of 18.7%. Again, MTB/RIF assay showed a sensitivity and specificity of 100% and 98%, respectively when compared with sputum culture, whereas smear microscopy, when compared with culture showed sensitivity and specificity of 44% and 98%, respectively. In TB/HIV co- infection, Xpert MTB/RIF assay showed a detection rate of 9.3% while Smear microscopy showed a lower rate of 4.9% out of the 126 HIV positive cases. This could be attributed to the fact that people with compromised immune system often release fewer organisms into their sputum at concentration below threshold for visual detection under the microscope. Therefore, it is concluded that Xpert MTB/RIF test has the potential to improve the diagnosis of Tuberculosis.