title: A comparison between the efficiency of the Xpert MTB/RIF assay and nested PCR in identifying Mycobacterium tuberculosis during routine clinical practice.
abstract: OBJECTIVE
  Polymerase chain reaction (PCR) for the detection of Mycobacterium tuberculosis (MTB) is more sensitive, specific, and rapid than the conventional methods of acid-fast bacilli (AFB) smear and culture. The aim of this study was to determine if the Xpert MTB/rifampicin (RIF) assay had additional advantages over nested PCR for the detection of MTB in a geographical area with intermediate tuberculosis (TB) incidence.
  
  
  METHODS
  Between February and December 2013, the Xpert MTB/RIF assay and MTB nested PCR, as well as AFB smear and culture, were simultaneously performed on 198 clinical samples (160 pulmonary and 38 non-pulmonary specimens) collected from 171 patients hospitalized at Hallym University Medical Center for possible TB. The accuracy of the diagnosis of MTB culture-positive TB and the turnaround time of reporting laboratory results were calculated and compared. Rifampin resistance by the Xpert MTB/RIF assay was reviewed with that of conventional drug susceptibility testing (DST).
  
  
  RESULTS
  The sensitivity, specificity, and positive and negative predictive values of the Xpert MTB/RIF assay and MTB nested PCR for diagnosis of MTB culture-positive pulmonary TB were 86.1% vs. 69.4% (P=0.1563), 97.8% vs. 94.1% (P=0.2173), 91.2% vs. 75.8% (P=0.1695), and 96.4% vs. 92.0% (P=0.2032), respectively. The median turnaround times of the Xpert MTB/RIF assay and MTB nested PCR were 0 [0-4] days and 4 [1-11] days, respectively (P<0.001). Two cases of rifampin resistance, as determined by the Xpert MTB/RIF assay, were found to be multi-drug resistant (MDR) pulmonary TB by DST.
  
  
  CONCLUSIONS
  The Xpert MTB/RIF assay seemed to be sensitive, specific, and comparable to nested PCR for identifying MTB among clinically suspected TB patients, and the assay can be valuable in giving a timely identification of resistance to rifampin.
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Cheol-Hong
authors: CH
authors: Kim
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Heungjeong
authors: H
authors: Woo
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: In Gyu
authors: IG
authors: Hyun
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Changhwan
authors: C
authors: Kim
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Jeong-Hee
authors: JH
authors: Choi
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Seung-Hun
authors: SH
authors: Jang
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Sang Myeon
authors: SM
authors: Park
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Dong-Gyu
authors: DG
authors: Kim
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Myung Goo
authors: MG
authors: Lee
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Ki-Suck
authors: KS
authors: Jung
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Jeongwon
authors: J
authors: Hyun
authors: 1 Department of Internal Medicine, 2 Lung Research Institute, 3 Department of Laboratory Medicine, Hallym University College of Medicine, Chuncheon, Korea.
authors: Hyun Soo
authors: HS
authors: Kim
keywords: Mycobacterium tuberculosis (MTB); polymerase chain reaction (PCR); pulmonary tuberculosis