Isothermal target and probe amplification for Mycobacterium tuberculosis identification from broth cultures.

SETTING: Various methods are used to identify Mycobacterium tuberculosis complex (MTC) from broth cultures. The isothermal target and probe amplification (iTPA) method has recently been introduced as a simple and cost-effective molecular assay. OBJECTIVE: To evaluate the diagnostic performance of the iTPA method. DESIGN: A total of 175 specimens from the Mycobacteria Growth Indicator Tube (MGIT) 960 broth culture system were evaluated. The immunochromatographic test (ICT) and real-time quantitative PCR (RQ-PCR) were compared with the iTPA method. RESULTS: MTC was identified in 71/131 MGIT-positive specimens, including 60 ICT-positive and 11 ICT- negative/PCR-positive specimens. The sensitivity and specificity of the ICT assay were respectively 84.5% (95%CI 74.0-92.0) and 100% (95%CI 94.0-100). These 71 specimens were all MTC-positive with the iTPA method also. Sixty non-tuberculous mycobacteria specimens and 44 MGIT-negative specimens were all MTC-negative with the iTPA method. CONCLUSION: Our data show that the diagnostic performance of the iTPA method is comparable to that of RQ-PCR. The iTPA method could be a reliable and cost-effective option for the identification of MTC from broth culture.