The diagnostic accuracy of the MTBDRplus and MTBDRsl assays for drug-resistant TB detection when performed on sputum and culture isolates.

Michele Tomasicchio,Grant Theron,Keertan Dheda,Elizabeth Streicher,Elize Pietersen,Rob Warren,Paul Van Helden,Danielle Stanley-Josephs

doi:10.1038/srep17850

Abstract

Although molecular tests for drug-resistant TB perform well on culture isolates, their accuracy using clinical samples, particularly from TB and HIV-endemic settings, requires clarification. The MTBDRplus and MTBDRsl line probe assays were evaluated in 181 sputum samples and 270 isolates from patients with culture-confirmed drug-sensitive-TB, MDR-TB, or XDR-TB. Phenotypic culture-based testing was the reference standard. Using sputum, the sensitivities for resistance was 97.7%, 95.4%, 58.9%, 61.6% for rifampicin, isoniazid, ofloxacin, and amikacin, respectively, whereas the specificities were 91.8%, 89%, 100%, and 100%, respectively. MTBDRsl sensitivity differed in smear-positive vs. smear-negative samples (79.2% vs. 20%, p < 0.0001 for ofloxacin; 72.9% vs. 37%, p = 0.0023 for amikacin) but not by HIV status. If used sequentially, MTBDRplus and MTBDRsl could rule-in XDR-TB in 78.5% (22/28) and 10.5% (2/19) of smear-positive and smear-negative samples, respectively. On culture isolates, the sensitivity for resistance to rifampicin, isoniazid, ofloxacin, and amikacin was 95.1%, 96.1%, 72.3% and 76.6%, respectively, whereas the specificities exceeded 96%. Using a sequential testing approach, rapid sputum-based diagnosis of fluoroquinolone or aminoglycoside-resistant TB is feasible only in smear-positive samples, where rule-in value is good. Further investigation is required in samples that test susceptible in order to rule-out second-line drug resistance.

Highlights

Tuberculosis (TB) remains a leading cause of morbidity and mortality in developing countries[42]
In contrast to testing methods like the nitrate reductase assay[14] and Microscopic Observation Drug Susceptibility (MODS)[15], the MTBDRplus line probe assay (LPA; Hain Lifescience, Nehren, Germany), which is approved by the World Health Organisation (WHO) for the detection of RIF and INH resistance, is a same day test with a short relatively rapid within laboratory turn-around-time (~5 hours)
To address these considerations we evaluated the comparative diagnostic accuracy of the MTBDRplus and MTBDRsl assays using smear-positive and smear-negative sputum samples, and culture isolates obtained from patients in a TB and HIV endemic setting

Summary

Introduction

Tuberculosis (TB) remains a leading cause of morbidity and mortality in developing countries[42]. In contrast to testing methods like the nitrate reductase assay[14] and Microscopic Observation Drug Susceptibility (MODS)[15], the MTBDRplus line probe assay (LPA; Hain Lifescience, Nehren, Germany), which is approved by the World Health Organisation (WHO) for the detection of RIF and INH resistance, is a same day test with a short relatively rapid within laboratory turn-around-time (~5 hours) It has an estimated sensitivity and specificity of 98.1% and 98.7% for both RIF and INH, when performed on culture isolates[16], there are limited data www.nature.com/scientificreports/. A sequential testing strategy to inform clinical practice (e.g. MTBDRplus followed by MTBDRsl), and determinants of performance in this context, has hitherto not been evaluated To address these considerations we evaluated the comparative diagnostic accuracy of the MTBDRplus and MTBDRsl assays using smear-positive and smear-negative sputum samples, and culture isolates obtained from patients in a TB and HIV endemic setting

Methods

Results

Conclusion