Background: The elimination of TB requires early, rapid and accurate diagnosis and treatment. TB mortality is mainly due to delayed diagnosis or misdiagnosis which also increases the possibility of TB transmission. Xpert MTB/RIF assay is a new rapid point- of-care test that can in 2 hours, simultaneously detect, Mycobacterium tuberculosis and rifampicin resistance and is capable of overcoming many of the current operational problems in TB diagnosis. Objective: to evaluate the usefulness of Xpert MTB/RIF test for early, rapid, and accurate diagnosis of pulmonary tuberculosis and to determine the added value of the assay to address patients' transmission potential in a fast, accurate and reliable manner. Methodology: Spot sputum samples collected at hospital presentation from fifty patients with symptoms and signs suggestive of pulmonary TB and / or who have suggestive TB chest x-ray, during the period from August 2017 to July 2018. All microbiological analyses were performed on the same sample after splitting it into two aliquots. One aliquot was tested by ZN staining and Xpert MTB/RIF assay and the other was cultured for isolation of TB bacilli by conventional method. Diagnostic performance was done for both ZN stained smear and XPERT MTB/RIF assay using culture as a reference standard. Results: Compared with culture, the sensitivity and the specificity of XPERT MTB/RIF assay were 100% and 75% respectively, PPV was 95.5%, NPV was 100% and there was very good (kappa = 0.834) agreement between both methods. Two samples tested positive by XPERT MTB/RIF though negative by culture and there was significant negative correlation between semi-quantitative results of XPERT MTB/RIF test expressed in cycle threshold values against grade of smear positivity. Conclusion: Xpert MTB/RIF assay had a very high sensitivity and specificity when compared to the reference standard method. It is a single test that is more effective than smear dependent strategies for both T.B diagnosis and evaluation of patient transmission potential. It can detect M. tuberculosis complex and rifampicin resistance in two hours. The assay is rapid, easy to perform with no technical difficulties. This new diagnostic method can lead to more cases of active TB to be detected, avoiding treatment delay, reduction in the transmission risk and improvement in TB control. |
