Evaluation of Xpert MTB/RIF for detection of tuberculosis from blood samples of HIV-infected adults confirms Mycobacterium tuberculosis bacteremia as an indicator of poor prognosis
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Tuberculosis (TB) remains a leading cause of death among HIV-infected adults, in part because of delayed diagnosis and therefore delayed initiation of treatment. Recently, the Gene-Xpert platform, a rapid, PCR-based diagnostic platform, has been validated for the diagnosis of TB with sputum. We have evaluated the Xpert MTB/RIF assay for the diagnosis of Mycobacterium tuberculosis bacteremia and investigated its impact on clinical outcomes. Consecutive HIV-infected adults with fever and cough presenting to Queen Elizabeth Central Hospital, Blantyre, Malawi, were recruited and followed up for 2 months. At presentation, three sputum samples were examined by smear, culture, and Xpert MTB/RIF assay for the presence of M. tuberculosis and blood was drawn for PCR with Xpert, for mycobacterial culture (Myco/F Lytic), and for aerobic culture. One hundred four patients were recruited, and 44 (43%) were sputum culture positive for M. tuberculosis. Ten were Xpert blood positive, for a sensitivity of 21% and a specificity of 100%. The 2-week mortality rate was significantly higher among patients who were Xpert blood positive than among those who were negative (40% versus 3%; multivariate odds ratio [OR] for death if positive, 44; 95% confidence interval [CI], 3 to 662). This effect persisted on assessment of the mortality rate at 2 months (40% versus 11%; OR, 5.6; 95% CI, 1.3 to 24.6). When screening uncomplicated patients presenting with a productive cough for pulmonary TB, Xpert blood offers no diagnostic advantage over sputum testing. Despite this, Xpert blood positivity is highly predictive of early death and this test rapidly identifies a group of patients in urgent need of initiation of treatment.
Feasey , N A , Banada , P P , Howson , W , Sloan , D J , Mdolo , A , Boehme , C , Chipungu , G A , Allain , T J , Heyderman , R S , Corbett , E L & Alland , D 2013 , ' Evaluation of Xpert MTB/RIF for detection of tuberculosis from blood samples of HIV-infected adults confirms Mycobacterium tuberculosis bacteremia as an indicator of poor prognosis ' Journal of Clinical Microbiology , vol 51 , no. 7 , pp. 2311-2316 . DOI: 10.1128/JCM.00330-13
Journal of Clinical Microbiology
Copyright © 2013 Feasey et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 3.0 Unported license.
DescriptionThe Foundation for Innovative New Diagnostics supported this study financially and had a role in its design, data interpretation, and writing of the manuscript (C.B.). N.A.F. and D.A. had full access to all study data and, in consultation with the rest of us, made the final decision to submit this work for publication. N.A.F. was funded by a Wellcome Research Training Fellowship. The surveillance service for invasive bacterial infections at the Malawi-Liverpool Wellcome Trust is supported by a Wellcome Trust Major Overseas Program award (084679/Z/08/Z).
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