title: Evaluation of Isothermal Target and Probe Amplification (iTPA) for the Detection of Mycobacterium Tuberculosis.
abstract: BACKGROUND
  This study compared the diagnostic power of isothermal target and probe amplification (iTPA) with the existing real-time PCR for the detection of Mycobacterium tuberculosis (MTB).
  
  
  METHODS
  The two molecular methods were performed using DNA extracted directly from lower respiratory tract samples, not from the culture broth. A total of 174 non-consecutive patients with suspected pulmonary tuberculosis were enrolled in this study. Acid-fast bacilli (AFB) stain and liquid culture with the BACTEC MGIT 960 system (Becton Dickinson Diagnostic, USA) were performed. Real-time PCR and iTPA methods were performed with the AdvanSure TB/NTM TaqMan assay (LG Lifescience, Korea) and the RapiDx® MTB test (RapleGene, Korea).
  
  
  RESULTS
  Among 174 patients, 49 of 52 isolates were identified as MTB and 3 of 52 isolates were identified as non-tuberculous mycobacteria NTM. Based on the culture results, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 95.9%, 90.1%, 81.3%, and 98.2% for iTPA, and 95.7%, 91.0%, 80.4%, and 98.2% for real-time PCR, respectively. The agreement of iTPA was 83.0% with the AFB stain, 92.4% with the MGIT culture, and 94.2% with real-time PCR. Disagreement between the two molecular methods occurred in 10 patients.
  
  
  CONCLUSIONS
  This study is the first to report the evaluation of iTPA conducted from direct specimens. Both iTPA and real-time PCR proved to be rapid, sensitive, and specific tools for the detection of MTB in clinical samples. The iTPA method for the MTB detection revealed a high concordance rate with real-time PCR.
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jehoon
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hi Jeong
authors.initials: HJ
authors.lastname: Kwon
authors.affiliation: Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Kwan Hyoung
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Chang Dong
authors.initials: CD
authors.lastname: Yeo
authors.affiliation: Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jin Woo
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea hkl@catholic.ac.kr.
authors.forename: Hae Kyung
authors.initials: HK
authors.lastname: Lee
mesh_terms: D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000382:microbiology
keywords: Mycobacterium tuberculosis; iTPA; isothermal; real-time PCR