Comparison of Xpert MTB/RIF with ProbeTec ET DTB and COBAS TaqMan MTB for direct detection of M. tuberculosis complex in respiratory specimens

Uladzimir Antonenka,Laziz Turaev,Ainura Esenalieva,Tarig Alnour,Mokhonim Abdulloeva,Evgeni Sahalchyk,Harald Hoffmann,Sabine Hofmann-Thiel

doi:10.1186/1471-2334-13-280

Abstract

BackgroundNucleic acid amplification assays allow for the rapid and accurate detection of Mycobacterium tuberculosis (MTB) directly in clinical specimens thereby facilitating diagnosis of tuberculosis (TB). With the fully automated Xpert MTB/RIF system (Cepheid) an innovative solution of TB diagnostics has been launched. We performed a direct head-to-head comparison of Xpert MTB/RIF with two widely used commercial assays, ProbeTec ET DTB (DTB) (Becton-Dickinson) and COBAS TaqMan MTB (CTM-MTB) (Roche).Methods121 pre-characterized respiratory specimens (68 culture-positive for MTB complex, 24 culture-positive for non-tuberculous mycobacteria and 29 culture-negative) taken from our frozen specimen bank were tested for the presence of MTB complex by the three assays.ResultsAmong culture-positive samples (n = 68), overall sensitivity for detection of MTB complex was 74.6%, 73.8%, and 79.1% for Xpert MTB/RIF, CTM-MTB, and DTB, respectively. Within the subgroup of smear-negative TB samples (n = 51) sensitivity was 68% for Xpert MTB/RIF and CTM-MTB and 72% for DTB. Among smear-positive TB samples (n = 17), all (100%) were detected by DTB and 94.1% and 93.3% by Xpert MTB/RIF and CTM-MTB, respectively. Specificity was best for CTM-MTB (100%) and lowest for Xpert MTB/RIF (96.2%) due to misidentification of two NTM samples as MTB complex. CTM-MTB yielded the highest rate of invalid results (4.1%) (0.8% by Xpert MTB/RIF and DTB, respectively).ConclusionsThe direct comparison of Xpert MTB/RIF with CTM-MTB and DTB yielded similar overall performance data. Whereas DTB was slightly superior to Xpert MTB/RIF in terms of sensitivity, at least in the sample collection tested here, CTM-MTB performed best in terms of specificity.

Highlights

Nucleic acid amplification assays allow for the rapid and accurate detection of Mycobacterium tuberculosis (MTB) directly in clinical specimens thereby facilitating diagnosis of tuberculosis (TB)
The Xpert MTB/RIF (Cepheid) represents the first assay which uses a fully integrated real-time PCR platform allowing the simultaneous detection of M. tuberculosis complex (MTBC) and resistance to rifampin (RMP) based on rpoB as target sequence [2]
The smear-positive TB sample which was not detected by Xpert MTB/RIF was of scanty grade in smear microscopy

Summary

Introduction

Nucleic acid amplification assays allow for the rapid and accurate detection of Mycobacterium tuberculosis (MTB) directly in clinical specimens thereby facilitating diagnosis of tuberculosis (TB). The introduction of nucleic acid amplification tests (NAAT) for detection of M. tuberculosis complex (MTBC) directly from clinical specimens has greatly improved tuberculosis (TB) diagnostics by giving results within one day. Such tests confirm the diagnosis of TB. A number of commercial assays are available which use different molecular approaches to amplify and detect MTBC These are, for example, COBAS TaqMan MTB (CTM-MTB) (Roche), Amplified M. tuberculosis Direct (AMTD) (GenProbe), ProbeTec ET DTB (DTB) (BectonDickinson), Mycobacterium tuberculosis Ligase Chain reaction (LCx) (Abott) or GenoType Mycobacteria Direct assay (GTMD) (HAIN Lifesciences). These data suggested that sensitivity might be superior to that of other commercial assays [4,5,6,7]

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