Non-Conforming Rifampicin Susceptibility Test Reports from Xpert MTB/RIF Assay: The National Reference Laboratory Experience in Nigeria
Nkiru N. Nwokoye , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
Chizoba C. Onubogu , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
Okechukwu P. Nwadike , KNCV/TB CARE1 project, Federal Capital Territory, Abuja, Nigeria.
Abigail T. Abiodun , National TB Reference Laboratory, Microbiology Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
Dan Onwujekwe , Clinical Sciences Division, Nigerian Institute of Medical Research, Lagos, Nigeria.
Mustapha Gidado , KNCV/TB CARE1 project, Federal Capital Territory, Abuja, Nigeria.
Olawale O. Olubi , Department of Ear Nose and throat, Lagos State University teaching Hospital, Ikeja, Lagos, Nigeria.
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
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