Clinical Usefulness of Real-time PCR and Amplicor MTB PCR Assays for Diagnosis of Tuberculosis

Abstract

Background: PCR assay has provided a mean of more rapid and sensitive detection of Mycobacterium tuberculosis (MTB) complex than conventional acidfast bacilli (AFB) smears and MTB cultures. Using the recently developed AdvanSure TB/NTM kit (LG Life Science Diagnostic Division, Korea), which could differentiate nontuberculous mycobacteria (NTM) from MTB, this study compared clinical usefulness of real-time PCR assay and Amplicor MTB PCR assay (Roche Molecular Systems, USA) for diagnosis of tuberculosis. Methods: A total of 213 specimens (148 respiratory and 65 nonrespiratory specimens) were tested by using real-time PCR, Amplicor MTB PCR, AFB smear, and MTB culture. The sensitivity and specificity of four methods were evaluated according to clinical diagnosis. Results: Of six NTM grown in culture, four (67%) were detected by real-time PCR. The overall agreement of real-time and Amplicor MTB PCR was 92% (191/207). The overall sensitivity and specificity were 91% and 87%, respectively, for real-time PCR, and 86% and 93% for Amplicor MTB PCR. In nonrespiratory specimens, the sensitivities of real-time PCR, Amplicor MTB PCR, AFB smear, and MTB culture were 67%, 60%, 13%, and 40%, respectively, and the specificity of the four methods were all 100%. Conclusion: For diagnosis of tuberculosis, the sensitivity and specificity of the real-time PCR assay using AdvanSure TB/NTM kit and Amplicor MTB PCR were similar, and the former could differentiate NTM from MTB. The PCR assay can be considered as a more sensitive technique for the detection of MTB than the conventional AFB smear and culture. (Korean J Clin Microbiol 2008;11:29-33)