Abstract
BackgroundThe WHO has recommended the implementation of rapid diagnostic tests to detect and help combat M/XDR tuberculosis (TB). There are limited data on the performance and impact of these tests in field settings.MethodsThe performance of the commercially available Genotype MTBDRplus molecular assay was compared to conventional methods including AFB smear, culture and drug susceptibility testing (DST) using both an absolute concentration method on Löwenstein-Jensen media and broth-based method using the MGIT 960 system. Sputum specimens were obtained from TB suspects in the country of Georgia who received care through the National TB Program.ResultsAmong 500 AFB smear-positive sputum specimens, 458 (91.6%) had both a positive sputum culture for Mycobacterium tuberculosis and a valid MTBDRplus assay result. The MTBDRplus assay detected isoniazid (INH) resistance directly from the sputum specimen in 159 (89.8%) of 177 specimens and MDR-TB in 109 (95.6%) of 114 specimens compared to conventional methods. There was high agreement between the MTBDRplus assay and conventional DST results in detecting MDR-TB (kappa = 0.95, p<0.01). The most prevalent INH resistance mutation was S315T (78%) in the katG codon and the most common rifampicin resistance mutation was S531L (68%) in the rpoB codon. Among 13 specimens from TB suspects with negative sputum cultures, 7 had a positive MTBDRplus assay (3 with MDR-TB). The time to detection of MDR-TB was significantly less using the MTBDRplus assay (4.2 days) compared to the use of standard phenotypic tests (67.3 days with solid media and 21.6 days with broth-based media).ConclusionsCompared to conventional methods, the MTBDRplus assay had high accuracy and significantly reduced time to detection of MDR-TB in an area with high MDR-TB prevalence. The use of rapid molecular diagnostic tests for TB and drug resistance should increase the proportion of patients promptly placed on appropriate therapy.
Highlights
The global emergence of multidrug-resistant (MDR) tuberculosis is an alarming issue in international tuberculosis (TB) control and presents an enormous challenge not yet sufficiently addressed [1]
The primary objective of our study was to assess the performance, impact, and time to detection of drug resistant TB of a rapid molecular diagnostic test compared to conventional culture and drug susceptibility testing (DST) methods when implemented into the normal workflow of a high volume National TB Reference Laboratory (NRL) which provides laboratory support for the Georgian National TB Program (NTP)
Between June and October 2009, all acid-fast bacilli (AFB) smear positive sputum specimens obtained from TB suspects without previous history of TB from throughout Georgia were consecutively enrolled into the study
Summary
The global emergence of multidrug-resistant (MDR) tuberculosis (resistance to isoniazid [INH] and rifampicin [RIF]) is an alarming issue in international tuberculosis (TB) control and presents an enormous challenge not yet sufficiently addressed [1]. The latest global surveillance data indicate the highest level of drug-resistance ever recorded with an estimated 440,000 MDRTB cases worldwide resulting in 150,000 deaths in 2009 [2]. MDR-TB has proven difficult to treat due to costly, complex, and less effective treatment regimens and is associated with significantly worse outcomes as compared to drug susceptible disease [3]. Of particular concern is that only an estimated 7% of all MDR-TB cases are detected [2]. Conventional AFB culture and drug susceptibility testing (DST) requires significant laboratory infrastructure and has a slow turnaround time which can result in delayed initiation of proper therapy and increasing risk of disease transmission and amplification of drug resistance due to initiation of inadequate treatment regimens [4]. There are limited data on the performance and impact of these tests in field settings
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
