Clostridium difficile is the most common infectious cause of nosocomial diarrhea, affecting thousands of patients annually and exacting enormous costs on the U.S. health care system. Early diagnosis is critical to prevent transmission and reduce morbidity and mortality, yet sensitive and specific diagnostic tests with a quick turnaround time are lacking. The objective of this study was to determine if a new commercially available real time polymerase chain reaction (PCR) test would prove more rapid, sensitive and specific than standard methods for the diagnosis of C. difficile infection (CDI). BD GeneOhm Cdiff assay, a real-time PCR assay for detection of C. difficile toxin B (tcdB) gene, was compared with Tox A/B II ELISA and a two-step algorithm which includes C. Diff Chek-60 Glutamate Dehydrogenase (GDH)-antigen assay followed by cytotoxin neutralization. Four-hundred liquid or semisolid stools submitted for diagnostic C. difficile testing were selected: 200 GDH antigen-positive and 200 GDH antigen-negative. All samples were tested by the C. Diff Chek-60 GDH antigen, cytotoxin neutralization, Toxin A/B II ELISA, and BD GeneOhm Cdiff assay. Discrepant specimens were tested by toxigenic culture as an independent gold standard. Chart review was performed on patients with discrepant specimens. As BD GeneOhm Cdiff assay was not FDA-cleared at the time of study, PCR results were not clinically reported. Of 200 GDH-positive samples, 71 were positive by Tox A/B II, 88 were positive by the two-step method, 93 were positive by PCR, and 96 were positive by GDH-antigen only. Of 200 GDH-negative samples, 3 were positive by PCR only. Toxigenic culture was performed on 41 samples with discrepant results and 39 were culture-positive. After culture resolution of discrepants, Tox A/B II detected 70 (66.7%), the two-step method detected 87 (82.9%), and PCR detected 96 (91.4%) of 105 true positives. The BD Gene-Ohm Cdiff assay was more sensitive in detecting toxigenic C. difficile than Tox A/B II (p <0.0001); however, the difference between PCR and the two-step method was not significant (p=0.1237). The BD GeneOhm Cdiff assay took a similar amount of time to perform as the Tox A/B II and was more rapid than the two-step method. Chart review revealed that 18 patients with cytotoxin-negative, PCR-positive discrepant samples were given 1-2 days of therapy (n=8), or no treatment at all (n=10). Yet symptoms resolved and no further C. difficile testing was requested for 13 of 18 patients for 6-8 months after hospital discharge. Only one patient had a subsequent cytotoxin positive stool submitted 22 days after the study sample was tested. Enhanced sensitivity and rapid turnaround time make the BD GeneOhm Cdiff assay an important advance in the diagnosis of toxigenic C. difficile infection. The BD GeneOhm Cdiff assay is significantly more sensitive than a commonly-used ELISA toxin assay and has a sensitivity and specificity comparable to the two-step method. Its turnaround time is similar to ELISA toxin assays and more rapid than the two-step method. Disadvantages to implementation of BD GeneOhm Cdiff assay include increased cost and potential treatment of asymptomatic carriers and mild, self-resolving disease.
| Identifer | oai:union.ndltd.org:YALE_med/oai:ymtdl.med.yale.edu:etd-02182010-164058 |
| Date | 27 July 2010 |
| Creators | Kvach, Elizabeth Jean |
| Contributors | Marie L. Landry, MD, John Howe, PhD |
| Publisher | Yale University |
| Source Sets | Yale Medical student MD Thesis |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://ymtdl.med.yale.edu/theses/available/etd-02182010-164058/ |
| Rights | unrestricted, I hereby grant to the Yale School of Medicine the non-exclusive license to photocopy, archive and make accessible, under the conditions specified below, my print and electronic thesis, in whole or in part, in all forms of media. <p> I agree that the Yale School of Medicine may electronically store, copy or translate my thesis to any medium or format for the purpose of preservation and accessibility. The Yale School of Medicine is not under obligation to reproduce or display my thesis in the same format in which it was originally deposited. <p> I retain all ownership rights to the thesis, including but not limited to the right to use in future works (such as articles and books) all or part of this thesis. |
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