Southern California Permanente Medical Group, North Hollywood, California 91605, USA.
J Clin Microbiol. 2010 Mar;48(3):889-93. doi: 10.1128/JCM.01801-09. Epub 2010 Jan 13.
The incidence of Clostridium difficile infection (CDI) has risen almost 3-fold in the United States over the past decade, emphasizing the need for rapid and accurate tests for CDI. The Cepheid Xpert C. difficile assay is an integrated, closed, nucleic acid amplification system that automates sample preparation and real-time PCR detection of the toxin B gene (tcdB). A total of 432 stool specimens from symptomatic patients were tested by a glutamate dehydrogenase (GDH) assay, a toxin A and B enzyme immunoassay (EIA), the Xpert C. difficile assay, and a cell culture cytotoxicity neutralization assay (CCCN). The results of these methods, used individually and in combination, were compared to those of toxigenic culture. Results for the Xpert C. difficile assay alone showed a sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of 94.4, 96.3, 84.0, and 98.8%, while the EIA alone gave corresponding values of 58.3, 94.7, 68.9, and 91.9%, respectively. An algorithm using the GDH assay and the EIA (plus the CCCN if the EIA was negative) showed corresponding values of 83.1, 96.7, 83.1, and 96.1%. The Xpert C. difficile assay was statistically superior to the EIA (P, <0.001 by Fisher's exact test) and to the GDH-EIA-CCCN algorithm (P, 0.0363). Combining the GDH and Xpert C. difficile assays lowered both the sensitivity and the NPV of the Xpert assay. The GDH-EIA-CCCN procedure required, on average, 2 days to complete testing on GDH-positive results, while testing by the Xpert C. difficile assay was completed, on average, in less than 1 h. Xpert C. difficile testing yielded the highest sensitivity and NPV, in the least amount of time, of the individual- and multiple-test algorithms evaluated in this study.
过去十年中，美国艰难梭菌感染（CDI）的发病率几乎增加了两倍，这强调了对 CDI 进行快速准确检测的必要性。Cepheid Xpert C. difficile 检测法是一种集成的、封闭的、核酸扩增系统，可自动进行样本制备和实时 PCR 检测毒素 B 基因（tcdB）。对 432 份来自有症状患者的粪便标本进行了谷氨酸脱氢酶（GDH）检测法、毒素 A 和 B 酶联免疫吸附试验（EIA）、Xpert C. difficile 检测法和细胞培养细胞毒性中和试验（CCCN）的检测。这些方法单独使用和联合使用的结果与产毒培养物的结果进行了比较。单独使用 Xpert C. difficile 检测法的结果显示，其敏感性、特异性、阳性预测值和阴性预测值（NPV）分别为 94.4%、96.3%、84.0%和 98.8%，而单独使用 EIA 的结果分别为 58.3%、94.7%、68.9%和 91.9%。使用 GDH 检测法和 EIA 的算法（如果 EIA 为阴性，则加上 CCCN）的结果分别为 83.1%、96.7%、83.1%和 96.1%。Xpert C. difficile 检测法在统计学上优于 EIA（Fisher 确切检验 P<0.001）和 GDH-EIA-CCCN 算法（P=0.0363）。同时联合使用 GDH 和 Xpert C. difficile 检测法降低了 Xpert 检测法的敏感性和 NPV。GDH-EIA-CCCN 程序平均需要 2 天才能完成对 GDH 阳性结果的检测，而 Xpert C. difficile 检测法的检测平均不到 1 小时即可完成。在本研究中评估的单个和多个检测算法中，Xpert C. difficile 检测法在最短的时间内获得了最高的敏感性和 NPV。
