Clinical Microbiology-Immunology Laboratories, University of North Carolina Hospitals, Chapel Hill, NC 27514, USA.
Anaerobe. 2009 Dec;15(6):270-3. doi: 10.1016/j.anaerobe.2009.10.005. Epub 2009 Oct 22.
There has been renewed interest in the laboratory diagnosis of Clostridium difficile infections due in large measure to the increase in both numbers and severity of cases of this disease. For the past two decades, enzyme-immunoassays (EIAs) for the detection of first C. difficile toxin A and then toxins A and B have been the most widely used diagnostic test for diagnosis of C. difficile infections. Recently this diagnostic approach has been called into question by the recognition that a screening test which detects glutamate dehydrogenase, a cell wall antigen of C. difficile, was significantly more sensitive than toxins A and B EIAs making it an effective screening test for C. difficile infection. Although sensitive, GDH lacks specificity and so if this test was utilized, a confirmatory test to differentiate false positives from true positives was needed. Studies to date have used cytotoxin neutralization or toxigenic culture as confirmatory tests but both of these have their limitations. A testing algorithm using rapid immunochromatographic devices for detection of GDH and toxins A and B as screening tests will give an accurate test result in approximately 90% of specimens within one hour when using cytotoxin neutralization as a reference method. For the other 10% of specimens, a third test would be needed in the algorithm. This test could be cytotoxin neutralization, toxigenic culture, or PCR for toxin or toxin operon genes.
由于这种疾病的病例数量和严重程度都在增加，人们对艰难梭菌感染的实验室诊断重新产生了兴趣。在过去的二十年中，用于检测第一种艰难梭菌毒素 A 然后是毒素 A 和 B 的酶免疫测定（EIAs）一直是诊断艰难梭菌感染的最广泛使用的诊断测试。最近，人们认识到，一种检测谷氨酸脱氢酶（艰难梭菌细胞壁抗原）的筛选试验比毒素 A 和 B EIAs 灵敏得多，这使得它成为一种有效的艰难梭菌感染筛选试验，从而对这种诊断方法提出了质疑。尽管灵敏，但 GDH 缺乏特异性，因此如果使用该测试，则需要一种确认测试来区分假阳性和真阳性。迄今为止的研究已经使用细胞毒素中和或产毒培养作为确认测试，但这两种测试都有其局限性。使用快速免疫层析设备检测 GDH 和毒素 A 和 B 作为筛选测试的测试算法，当使用细胞毒素中和作为参考方法时，将在大约 90%的标本中在一小时内给出准确的测试结果。对于另外 10%的标本，算法中还需要进行第三种测试。该测试可以是细胞毒素中和、产毒培养或用于毒素或毒素操纵子基因的 PCR。
