Qutub M O, AlBaz N, Hawken P, Anoos A
Departments Pathology and Laboratory Medicine, Medical Technologist, MBC: J-10, King Faisal Specialist Hospital and Research Centre, Jeddah-Branch, PO Box 40047, Jeddah 21499, Saudi Arabia.
Indian J Med Microbiol. 2011 Jul-Sep;29(3):293-6. doi: 10.4103/0255-0857.83916.
To evaluate usefulness of applying either the two-step algorithm (Ag-EIAs and CCNA) or the three-step algorithm (all three assays) for better confirmation of toxigenic Clostridium difficile. The antigen enzyme immunoassays (Ag-EIAs) can accurately identify the glutamate dehydrogenase antigen of toxigenic and nontoxigenic Clostridium difficile. Therefore, it is used in combination with a toxin-detecting assay [cell line culture neutralization assay (CCNA), or the enzyme immunoassays for toxins A and B (TOX-A/BII EIA)] to provide specific evidence of Clostridium difficile-associated diarrhoea.
A total of 151 nonformed stool specimens were tested by Ag-EIAs, TOX-A/BII EIA, and CCNA. All tests were performed according to the manufacturer's instructions and the results of Ag-EIAs and TOX-A/BII EIA were read using a spectrophotometer at a wavelength of 450 nm.
A total of 61 (40.7%), 38 (25.3%), and 52 (34.7%) specimens tested positive with Ag-EIA, TOX-A/BII EIA, and CCNA, respectively. Overall, the sensitivity, specificity, negative predictive value, and positive predictive value for Ag-EIA were 94%, 87%, 96.6%, and 80.3%, respectively. Whereas for TOX-A/BII EIA, the sensitivity, specificity, negative predictive value, and positive predictive value were 73.1%, 100%, 87.5%, and 100%, respectively. With the two-step algorithm, all 61 Ag-EIAs-positive cases required 2 days for confirmation. With the three-step algorithm, 37 (60.7%) cases were reported immediately, and the remaining 24 (39.3%) required further testing by CCNA. By applying the two-step algorithm, the workload and cost could be reduced by 28.2% compared with the three-step algorithm.
The two-step algorithm is the most practical for accurately detecting toxigenic Clostridium difficile, but it is time-consuming.
评估应用两步法算法（抗原酶免疫测定法[Ag-EIAs]和细胞系培养中和试验[CCNA]）或三步法算法（所有三种检测方法）更好地确认产毒艰难梭菌的实用性。抗原酶免疫测定法（Ag-EIAs）可准确识别产毒和不产毒艰难梭菌的谷氨酸脱氢酶抗原。因此，它与毒素检测试验[细胞系培养中和试验（CCNA）或毒素A和B的酶免疫测定法（TOX-A/BII EIA）]联合使用，以提供艰难梭菌相关性腹泻的特异性证据。
共对151份不成形粪便标本进行了Ag-EIAs、TOX-A/BII EIA和CCNA检测。所有检测均按照制造商的说明进行，Ag-EIAs和TOX-A/BII EIA的结果使用分光光度计在波长450nm处读取。
分别有61份（40.7%）、38份（25.3%）和52份（34.7%）标本经Ag-EIA、TOX-A/BII EIA和CCNA检测呈阳性。总体而言，Ag-EIA的敏感性、特异性、阴性预测值和阳性预测值分别为94%、87%、96.6%和80.3%。而TOX-A/BII EIA的敏感性、特异性、阴性预测值和阳性预测值分别为73.1%、100%、87.5%和100%。采用两步法算法时，所有61例Ag-EIAs阳性病例需要2天进行确认。采用三步法算法时，37例（60.7%）病例立即报告，其余24例（39.3%）需要通过CCNA进一步检测。与三步法算法相比，应用两步法算法可使工作量和成本降低28.2%。
两步法算法对于准确检测产毒艰难梭菌最为实用，但耗时较长。
