| Evaluation of the Xpert MTB/RIF assay for the diagnosis of pulmonary tuberculosis in a high HIV prevalence setting. | |
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MedLine Citation:
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PMID: 21493734 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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RATIONALE: Xpert MTB/RIF is a novel automated molecular diagnostic recently endorsed by the World Health Organization. However, performance-related data from high HIV prevalence settings are limited. OBJECTIVES: The impact of sample-related factors on performance and the significance of Xpert MTB/RIF-positive culture-negative discordance remain unclear. METHODS: Xpert MTB/RIF was evaluated using single archived spot-sputum samples from 496 South African patients with suspected TB. Mycobacterium tuberculosis culture positivity and phenotypic resistance to rifampicin served as reference standards. MEASUREMENTS AND MAIN RESULTS: Overall, Xpert MTB/RIF detected 95% (95% confidence interval [CI], 88-98%; 89 of 94) of smear-positive culture-positive cases and the specificity was 94% (91-96%; 320 of 339). The sensitivity in smear-negative cases was 55% (35-73%; 12 of 22) when the analysis was restricted to 1 ml of unprocessed sputum and culture time-to-positivity of less than or equal to 28 days. Compared with smear microscopy (n=94), Xpert MTB/RIF detected an additional 17 cases (n=111) representing an 18% (11-27%; 111 vs. 94) relative increase in the rapid TB case detection rate. Moreover, compared with smear microscopy, the inclusion of Xpert MTB/RIF-positive culture-negative TB cases (ruled-in by an alternative diagnostic method) resulted in the detection of a further 16 cases (n=127), thus significantly increasing the rapid TB case detection rate to 35% (95% CI, 26-45%; 94 to 111 vs. 94 to 127; P<0.01), the overall specificity to 99.1% (97-100%; 320 of 323; P<0.001), and sensitivity in smear-negative TB to 60% (P=0.12). Performance strongly correlated with smear status and culture time-to-positivity. In patients infected with HIV compared with patients uninfected with HIV Xpert MTB/RIF showed a trend to reduced sensitivity (P=0.09) and significantly reduced negative predictive value (P=0.01). The negative predictive value for rifampicin resistance was 99.4%. CONCLUSIONS: XpertMTB/RIF outperformed smear microscopy, established a diagnosis in a significant proportion of patients with smear-negative TB, detected many highly likely TB cases missed by culture, and accurately ruled out rifampicin-resistant TB. Sample-specific factors had limited impact on performance. Performance in patients infected with HIV, especially those with advanced immunosuppression, warrants further study. |
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Authors:
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Grant Theron; Jonny Peter; Richard van Zyl-Smit; Hridesh Mishra; Elizabeth Streicher; Samuel Murray; Rodney Dawson; Andrew Whitelaw; Michael Hoelscher; Surendra Sharma; Madhukar Pai; Robin Warren; Keertan Dheda |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2011-04-14 |
Journal Detail:
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Title: American journal of respiratory and critical care medicine Volume: 184 ISSN: 1535-4970 ISO Abbreviation: Am. J. Respir. Crit. Care Med. Publication Date: 2011 Jul |
Date Detail:
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Created Date: 2011-07-08 Completed Date: 2011-09-13 Revised Date: 2012-01-25 |
Medline Journal Info:
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Nlm Unique ID: 9421642 Medline TA: Am J Respir Crit Care Med Country: United States |
Other Details:
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Languages: eng Pagination: 132-40 Citation Subset: AIM; IM |
Affiliation:
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Lung Infection and Immunity Unit, Division of Pulmonology and UCT Lung Institute, Department of Medicine, University of Cape Town, Cape Town, South Africa. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adolescent Adult Aged Aged, 80 and over Antitubercular Agents / pharmacology Bacterial Proteins / genetics Drug Resistance, Bacterial Female HIV Infections / complications*, epidemiology Humans Male Middle Aged Molecular Diagnostic Techniques* Mycobacterium tuberculosis / drug effects, genetics Polymerase Chain Reaction Predictive Value of Tests Prevalence Rifampin / pharmacology Sensitivity and Specificity Tuberculosis, Multidrug-Resistant / diagnosis Tuberculosis, Pulmonary / complications*, diagnosis* Young Adult |
| Grant Support | |
ID/Acronym/Agency:
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//Canadian Institutes of Health Research |
| Chemical | |
Reg. No./Substance:
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0/Antitubercular Agents; 0/Bacterial Proteins; 0/rpoB protein, Mycobacterium tuberculosis; 13292-46-1/Rifampin |
| Comments/Corrections | |
Comment In:
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Am J Respir Crit Care Med. 2011 Dec 15;184(12):1420; author reply 1420
[PMID:
22174115
]
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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