Xpert MTB/RIF performance to diagnose tuberculosis and rifampicin resistance in a reference centre in southern Brazil

Abstract

Effective treatment of tuberculosis (TB) remains a serious public health problem in many countries, including Brazil, especially when considering drug-resistant disease. Xpert MTB/RIF has been implemented in many countries to reduce the time to TB diagnosis and to rapidly detect rifampicin resistance. The study aimed to describe and evaluate Xpert MTB/RIF performance in diagnosing pulmonary TB and rifampicin resistance in a tertiary healthcare facility in Brazil.A cross-sectional study was performed, which included all isolates of confirmed pulmonary TB patients from 2015 to 2018. Both Xpert MTB/RIF and GenoType MTBDRplus assays were performed to detect rifampicin and isoniazid resistance. In addition, isolates with detected resistance to rifampicin and/or isoniazid were analysed by phenotypic testing using MGIT-960 SIRE kit and whole-genome sequencing (WGS) using Illumina MiSeq Sequencing System.2148 respiratory specimens tested with Xpert MTB/RIF were included: n=1556 sputum, n=348 bronchoalveolar lavage and n=244 gastric washing. The overall Xpert MTB/RIF sensitivity in sputum was 94% and the overall specificity was 98%. The negative predictive value in sputum of all the patients was 99% with a positive predictive value of 89%. The concordance between Xpert MTB/RIF and phenotypic susceptibility test was 94.1%, while its concordance with WGS was 78.9%.Xpert MTB/RIF is a rapid and accurate diagnostic strategy for pulmonary TB, which can contribute to improvement in TB control. However, detection of rifampicin resistance might be associated with false-positive results.

Discordant results of Xpert MTB/Rif assay and BACTEC MGIT 960 liquid culture to detect Mycobacterium tuberculosis in community screening in Vietnam

“…The discordance rate of Xpert–MGIT results found in this study is higher than reported in studies done in clinical settings that included symptomatic patients who sought care in health centers or were diagnosed with TB in Brazil (20%) [ 13 ], South Africa (15%) [ 11 ] and South Korea (26%) [ 12 ]. In contrast, our study regarded active case finding in the general population.…”

“…Xpert is an automated within-cartridge PCR that produces results within two hours. Numerous studies have shown that Xpert performs well compared with liquid culture for symptomatic patients in clinical settings, with its sensitivity to detect Mycobacterium tuberculosis (MTB) ranging from 82 to 95% [ 10 – 13 ].…”

Epidemiology of first-and second-line anti-tuberculosis drug resistance in new pulmonary tuberculosis cases in Addis Ababa metropolitan area, Ethiopia

“…Although the primary objective of this study was not to validate rapid molecular testing against the reference standard method, we compared the rate of RR-TB detected using GeneXpert MTB/RIF Assay with BD BACTEC TM MGIT TM 960 SIRE liquid culture system for automated drug susceptibility testing. The sensitivity of 100% of GeneXpert MTB/RIF Assay in detecting rifampicin resistance in our study was in line with previous studies reported by Meawed TE et al, (100%; [62] in Egypt, Jahan H et al, (98.5%; 2016) [63] in Bangladesh, Pandey P et al, (98.6%; 2017) [64] in Nepal and Mekkaoui L et al, (100%; 2021) [65] in Belgium; but higher than the sensitivity reported in previous studies by Tang T et al, (84.0%; 2017) [66] in China and Feliciano CS et al, (94%; 2019) [67] in Brazil. Whereas, the specificity of 94.6% of GeneXpert MTB/RIF Assay in detecting rifampicin resistance in our study was lower than previous study reported by Meawed TE et al, (100%; [62] in Egypt, Jahan H et al, (100%; 2016) [63] in Bangladesh, Pandey P et al, (100%; 2017) [64] in Nepal, Mekkaoui L et al, (99.2%; 2021) [65] in Belgium and Feliciano CS et al, (98%; 2019) [67] in Brazil; but higher than the specificity reported by Tang T et al, (87.8%; 2017) [66] in China.…”

Development and validation of a multiplex real-time qPCR assay using GMP-grade reagents for leprosy diagnosis

“…However, as PCR was further developed, it became more affordable, versatile and reliable, with fully automated systems becoming commercially available from different companies [8][9][10]. For tuberculosis, routine tests using PCR reduced the turnaround time, allowing same day treatment initialization, which might impact resistance prevalence [11][12][13]. Cost-effective nucleic acid detection assays are relatively widespread, but assays for some neglected diseases are still missing.…”