Ciftçi Ihsan Hakkı, Aslan Mehtap Hülya, Aşık Gülşah
Afyonkarahisar University Faculty of Medicine, Department of Medical Microbiology, Afyonkarahisar, Turkey.
Mikrobiyol Bul. 2011 Jan;45(1):43-7.
Tuberculosis is still a major global health problem. Nowadays nucleic acid amplification tests which are recommended by the World Health Organization (WHO) become popular methods for the rapid detection of Mycobacterium tuberculosis complex (MTC). Recently introduced commercial Xpert MTB/RIF (Cepheid, USA) system is also a molecular method based on real-time polymerase chain reaction for simultaneous detection of both MTC and rifampicin resistance in the clinical sample. The sample processing, nucleic acid extraction, amplification and detection of known mutations related to rifampicin resistance are performed in a single cartridge in this integrated system and the results are obtained in two hours. The aim of this study was to evaluate the performance of Xpert MTB/RIF system for the detection of M.tuberculosis in pre-processed clinical samples by comparing the results obtained by Bactec 460TB 12B (BD Diagnostic, USA), Löwenstein-Jensen (LJ) culture and direct microscopy of smears stained with Ziehl- Neelsen (ZN). A total of 85 clinical specimens (50 sputum, 25 bronchoalveolar lavage, five thorasynthesis fluid and five urine samples) obtained from tuberculosis-suspected patients were included to the study. All specimens were decontaminated and this decontaminated suspension was used in the diagnostic methods, except for Xpert MTB/RIF process. Twenty-five (29%) of the samples yielded positive result with Bactec 460TB, 25 (29%) were found positive with Xpert MTB/RIF, 15 (18%) were found positive with LJ and 11 (13%) were found positive with ZN staining method. High consistency was detected between the results of Bactec 460TB and Xpert MTB/RIF when Bactec 460TB was considered as the gold standard method (r= 0.943; p= 0.000). One specimen yielded false positive result with Xpert MTB/RIF when compared to the reference method. The sensitivity, specificity, positive and negative predictive values of Xpert MTB/RIF test were then estimated as 96%, 98%, 96% and 98%, respectively. No resistance were detected for the tested isolates. This study suggested that the sensitivity of Xpert MTB/RIF system in direct detection of M.tuberculosis in smear positive and smear negative samples was consistent with the reference methods. Moreover, the MTB/RIF test provided sensitive detection of tuberculosis in less than two hours.
结核病仍然是一个重大的全球健康问题。如今，世界卫生组织（WHO）推荐的核酸扩增检测已成为快速检测结核分枝杆菌复合群（MTC）的常用方法。最近推出的商用Xpert MTB/RIF（美国赛沛公司）系统也是一种基于实时聚合酶链反应的分子方法，用于同时检测临床样本中的MTC和利福平耐药性。在这个集成系统中，样本处理、核酸提取、扩增以及与利福平耐药性相关的已知突变的检测都在一个单一的试剂盒中进行，并且在两小时内就能获得结果。本研究的目的是通过比较Bactec 460TB 12B（美国BD诊断公司）、罗氏培养基（LJ）培养以及萋尼氏（ZN）染色涂片直接显微镜检查所得到的结果，来评估Xpert MTB/RIF系统在检测预处理临床样本中结核分枝杆菌方面的性能。本研究纳入总计85份从疑似结核病患者获取的临床标本（50份痰液、25份支气管肺泡灌洗液、5份胸腔积液和5份尿液样本）。除了Xpert MTB/RIF检测流程外，所有标本均进行了去污处理，并且将这种去污后的悬液用于诊断方法检测。25份（29%）样本通过Bactec 460TB检测呈阳性，25份（29%）通过Xpert MTB/RIF检测呈阳性，15份（18%）通过LJ检测呈阳性，11份（13%）通过ZN染色法检测呈阳性。当将Bactec 460TB视为金标准方法时，Bactec 460TB与Xpert MTB/RIF的结果之间检测到高度一致性（r = 0.943；p = 0.000）。与参考方法相比，有1份标本通过Xpert MTB/RIF检测得出假阳性结果。随后估计Xpert MTB/RIF检测的敏感性、特异性、阳性预测值和阴性预测值分别为96%、98%、96%和98%。在所检测的分离株中未检测到耐药性。本研究表明，Xpert MTB/RIF系统在直接检测涂片阳性和涂片阴性样本中的结核分枝杆菌时，其敏感性与参考方法一致。此外，MTB/RIF检测能在不到两小时内实现对结核病的灵敏检测。
