Non-Conforming Rifampicin Susceptibility Test Reports from Xpert MTB/RIF Assay: The National Reference Laboratory Experience in Nigeria
[1]
Nkiru N. Nwokoye , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
[2]
Chizoba C. Onubogu , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
[3]
Okechukwu P. Nwadike , KNCV/TB CARE1 project, Federal Capital Territory, Abuja, Nigeria.
[4]
Abigail T. Abiodun , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
[5]
Dan Onwujekwe , Clinical Sciences Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
[6]
Mustapha Gidado , KNCV/TB CARE1 project, Federal Capital Territory, Abuja, Nigeria.
[7]
Olawale O. Olubi , Department of Ear Nose and throat, Lagos State University teaching Hospital, Ikeja, Lagos, Nigeria.
[8]
Oni E. Idigbe , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
GeneXpert MTB/RIF assay is a technology that allows for the simultaneous detection of Mycobacterium tuberculosis complex and rifampicin resistance in a single reaction. Detection of rifampicin resistance and indeterminate results is based on a predetermined standard parameters derived from the cycle threshold values of the probes. Test reports that fail to conform to the set standard are generally non-reliable. This study is aimed at highlighting the rifampicin resistance and indeterminate results that failed to conform to the standard parameter values stated by the assay manufacturers. A retrospective review of archived Xpert results was carried out to scrutinize for discrepancies between the assay report and the standard parameter values. Discrepant test reports were selected and analysed. Out of 1,046 test reports reviewed, 5 failed to conform to the standard parameter values. Three of the non-conformed results were rifampicin resistance while two were associated with rifampicin indeterminate results. Since initiation of drug-resistant tuberculosis treatment in Nigeria, is based on the result of Xpert assay, withholding treatment for patient with non-conforming rifampicin susceptibility result until phenotypic drug susceptibility test report is out is highly recommended. This is to curtail the adverse effects of misdiagnosis on not just the patient, but on the TB program and the community at large.
Mycobacterium Tuberculosis, Rifampicin Resistance, Xpert MTB/RIF, Cycle Threshold, Hybridization Probe
[1]
Helb D, Jones M, Story E, et al. Rapid detection of Mycobacterium tuberculosis and rifampin resistance by use of on-demand, near-patient technology. J Clin Microbiol 2010;48:229-237
[2]
Van Rie A, Page-Shipp L, Scott L, et al. Xpert MTB/RIF for point-of-care diagnosis of TB in high HIV burden, resource limited countries: hype or hope? Expert Rev Mol Diagn 2010;10(7):937-946
[3]
Ioannidis P, Papaventsis D, Karabela S, et al. Cepheid GeneXpert MTB/RIF assay for Mycobacterium tuberculosis detection and rifampin resistance identification in patients with substantial clinical indications of tuberculosis and smear-negative microscopy results. J.Clin. Microbiol. 2011; 49(8): 3068-3070
[4]
Blakemore R, Story E, Helb D, et al. Evaluation of the analytical performance of the Xpert MTB/RIF assay. J Clin Microbiol 2010;48(7):2495-501
[5]
Van Der Zanden AG, Te Koppele-Vije EM, Vijaya Bhanu N, et al. Use of DNA extracts from Ziehl- Neelsen-stained slides for molecular detection of rifampin resistance and spoligotyping of Mycobacterium tuberculosis. J Clin Microbiol 2003;41:1101-1108
[6]
Steingart KR, Sohn H, Schiller I, et al. Xpert® MTB/RIF assay for pulmonary tuberculosis and rifampicin resistance in adults. Cochrane Database of Systematic Reviews 2013;Issue 1
[7]
Piatek AS, Telenti A, Murray MR, et al. Genotypic analysis of Mycobacterium tuberculosis in two distinct populations using molecular beacons: implications for rapid susceptibility testing. Antimicrob Agents Chemother 2000;44(1):103-10
[8]
Lawn SD, Nicol MP. Xpert®MTB/RIF assay: development, evaluation and implementation of a new rapid molecular diagnostic for tuberculosis and rifampicin resistance. Future Microbiol 2011;6:1067-1082
[9]
Tyagi S, Kramer FR. Molecular beacons: probes that fluoresce upon hybridization. Nat Biotechnol 1996;14:303–308
[10]
Piatek AS, Tyagi S, Pol AC, et al. Molecular beacon sequence analysis for detecting drug resistance in Mycobacterium tuberculosis. Nat Biotechnol 1998;16:359–363
[11]
Somoskovi A, Deggim V, Ciardo D, et al. Diagnostic implicationsof inconsistent results obtained with Xpert MTB/RIF assay in detection of Mycobacterium tuberculosis isolates with an rpoB mutation associated with low-level rifampin resistance. J Clin Microbiol 2013;51(9):3127-3129
[12]
Boehme CC, Nicol MP, Nabeta P, et al. Feasibility, diagnostic accuracy, and effectiveness of decentralised use of the Xpert MTB/RIF test for diagnosis of tuberculosis and multidrug resistance: a multicentre implementation study. Lancet 2011;377:1495-1505
[13]
Moure R, Munoz L, Torres M, et al. Rapid detection of Mycobacterium tuberculosis complex and rifampin resistance in smear-negative clinical samples by use of an integrated real-time PCR method. J Clin Microbiol 2011; 49:1137-39
[14]
Nicol MP, Workman L, Isaacs W, et al. Accuracy of the Xpert MTB/RIF test for the diagnosis of pulmonary tuberculosis in children admitted to hospital in Cape Town, South Africa: a descriptive study. Lancet Infect Dis. 2011;11:819-24
[15]
Marlowe EM, Novak-Weekley SM, Cumpio J, et al. Evaluation of the cepheid Xpert MTB/RIF assay for direct detection of Mycobacterium tuberculosis complex in respiratory specimens. J Clin Microbiol 2011;49:1621-1623
[16]
Armand S, Vanhuls P, Delcroix G, et al. Comparison of the Xpert MTB/RIF test with an IS6110-TaqMan real-time PCR assay for direct detection of Mycobacterium tuberculosis in respiratory and non respiratory specimens. J Clin Microbiol 2011; 49:1772-1776
[17]
Theron G, Peter J, van Zyl-Smit R, et al. Evaluation of the Xpert MTB/RIF assay for the diagnosis of pulmonary tuberculosis in a high HIV prevalence setting. Am J Respir Crit Care Med 2011;184:132-140
[18]
Federal Ministry of Health, Department of Public Health, National tuberculosis and leprosy control programme. Guidelines for the clinical management and control of drug resistant tuberculosis in Nigeria. Federal Republic of Nigeria, July 2011 ; Pg 32-58
[19]
Cepheid (2009). Cepheid brochure: Xpert®Mtb/RIF. Two-hour detection of MTB and resistance to rifampicin. Available: Http://www.cepheid.com/
