Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
J Clin Microbiol. 2013 Oct;51(10):3225-7. doi: 10.1128/JCM.01335-13. Epub 2013 Jul 17.
The Xpert MTB/RIF assay (Cepheid, Sunnyvale, CA) is a fully automated, cartridge-based real-time PCR assay designed to detect Mycobacterium tuberculosis and rifampin resistance within 2 h. The performance of the Xpert assay has been evaluated in various clinical settings. However, there are few data comparing the Xpert assay to the Cobas TaqMan MTB test (Roche Diagnostics, Basel, Switzerland), one of the most widely utilized molecular assays for M. tuberculosis detection. In this prospective study, 320 consecutive respiratory specimens were processed simultaneously using acid-fast bacillus (AFB) staining, mycobacterial cultures with both solid and liquid media, and the Cobas and Xpert assays. The Xpert assay was performed with direct respiratory specimens, while the Cobas assay was done with decontaminated concentrated specimens. Based on the culture as a reference method, the overall sensitivities of the Cobas and Xpert assays were 71.4% and 67.9%, respectively. When AFB smear results were taken into consideration, the sensitivities of the Cobas assay for smear-positive and -negative specimens were 87% and 54%, while those of the Xpert assay were 67% and 69%, respectively. The Cobas assay showed 100% specificity and 100% positive predictive value (PPV) regardless of smear results, while the Xpert assay showed 100% specificity and 100% PPV for smear-positive specimens but 98% specificity and 60% PPV for smear-negative specimens. In conclusion, the Xpert assay showed performance that was slightly inferior to that of the Cobas assay but seems useful for the rapid detection of M. tuberculosis, considering that it was performed without laborious and time-consuming decontamination and concentration procedures.
Xpert MTB/RIF assay（Cepheid，加利福尼亚州森尼韦尔）是一种完全自动化的基于盒式的实时 PCR 检测方法，旨在 2 小时内检测结核分枝杆菌和利福平耐药性。该 Xpert 检测方法已在各种临床环境中进行了评估。然而，与最广泛用于结核分枝杆菌检测的 Cobas TaqMan MTB 检测（罗氏诊断公司，瑞士巴塞尔）相比，比较该 Xpert 检测方法的研究数据较少。在这项前瞻性研究中，同时使用抗酸杆菌（AFB）染色、固体和液体培养基培养分枝杆菌以及 Cobas 和 Xpert 检测方法处理了 320 例连续的呼吸道标本。Xpert 检测方法直接使用呼吸道标本进行，而 Cobas 检测方法则使用经过消毒的浓缩标本进行。基于培养作为参考方法，Cobas 和 Xpert 检测方法的总体敏感性分别为 71.4%和 67.9%。当考虑 AFB 涂片结果时，Cobas 检测方法对涂片阳性和阴性标本的敏感性分别为 87%和 54%，而 Xpert 检测方法的敏感性分别为 67%和 69%。无论 AFB 涂片结果如何，Cobas 检测方法的特异性和阳性预测值（PPV）均为 100%，而 Xpert 检测方法的特异性和 PPV 对涂片阳性标本为 100%和 100%，但对涂片阴性标本为 98%和 60%。总之，Xpert 检测方法的性能略逊于 Cobas 检测方法，但考虑到它无需繁琐且耗时的消毒和浓缩程序，对于快速检测结核分枝杆菌似乎有用。
