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Analysis of Discordance between Genotypic and Phenotypic Assays for Rifampicin Resistant Mycobacterium tuberculosis Isolated from Healthcare Facilities in Mthatha
Bokop, C.; Faye, L.M.; Apalata, T. Analysis of Discordance between Genotypic and Phenotypic Assays for Rifampicin-Resistant Mycobacterium tuberculosis Isolated from Healthcare Facilities in Mthatha. Pathogens2023, 12, 909.
Bokop, C.; Faye, L.M.; Apalata, T. Analysis of Discordance between Genotypic and Phenotypic Assays for Rifampicin-Resistant Mycobacterium tuberculosis Isolated from Healthcare Facilities in Mthatha. Pathogens 2023, 12, 909.
Bokop, C.; Faye, L.M.; Apalata, T. Analysis of Discordance between Genotypic and Phenotypic Assays for Rifampicin-Resistant Mycobacterium tuberculosis Isolated from Healthcare Facilities in Mthatha. Pathogens2023, 12, 909.
Bokop, C.; Faye, L.M.; Apalata, T. Analysis of Discordance between Genotypic and Phenotypic Assays for Rifampicin-Resistant Mycobacterium tuberculosis Isolated from Healthcare Facilities in Mthatha. Pathogens 2023, 12, 909.
Abstract
The study sought to determine the rate of discordant results between genotypic and phe-notypic tests for the diagnosis of drug resistant tuberculosis (DR-TB). Sputum samples and cultured isolates from suspected DR-TB patients were respectively analysed for My-cobacterium tuberculosis by Xpert® MTB/RIF (Cepheid, USA) and Line Probe Assays (LPA) (Hain, Germany). Discrepant Rifampicin (RMP) resistant results were confirmed using BACTEC MGIT960 (BD, USA). Of 224 RMP-resistant by Xpert MTB/RIF, 5.4% were suscep-tible to RMP by LPA. MGIT960 showed 75% agreement with LPA. Discrepancy was at-tributed to either heteroresistance or DNA contamination during LPA testing in 58.3% of cases. In 25% of samples showing agreement in RMP resistance between Xpert MTB/RIF and MGIT960, discrepancy was attributed to laboratory errors causing false RMP suscep-tible results with LPA. Of 16.7% of cases, discrepancy was attributed to false RMP suscep-tible results with Xpert MTB/RIF. Of 224 isolates, susceptibility to isoniazid (INH) by LPA was performed in 73.7% RMP resistant isolates, of which, 80.6% were resistant. All RMP resistant isolates by Xpert MTB/RIF were confirmed in 98.5% by LPA if TB isolates were resistant to INH, but only confirmed in 81.3% if TB isolates were INH susceptible (ρ < 0.001). In conclusion, Laboratory errors should be considered when investigating dis-cordant results.
Medicine and Pharmacology, Epidemiology and Infectious Diseases
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