College of American Pathologists
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CAP Today




July 2010

Letter C. difficile detection

The article “Smart choice for C. diff detection—PCR” (May 2010, page 1) provided an excellent review of the new PCR assays that are available for detecting toxigenic Clostridium difficile in stool. The commercialization of these PCR assays has made it possible for more laboratories to do molecular testing for C. diff.

While the article provided a comprehensive review of the PCR options available, it did not discuss other molecular methods that will soon be available for C. difficile testing. I recently had the opportunity to conduct a C. diff detection study using Illumigene C. difficile (Meridian Bioscience), a molecular C. diff test based on LAMP (Loop Mediated Isothermal Amplification) technology that is currently awaiting Food and Drug Administration approval.

In the course of our study, we compared the LAMP-based C. difficile assay to both culture and cytotoxin assays. We found that the LAMP-based assay performed very well, with a sensitivity and specificity extremely comparable to that of a number of other PCR-based assays we have seen. Additionally, we observed a poster from D. J. Mayne and M. Tubban of Sacred Heart Hospital in Pensacola, Fla., at the recent American Society for Microbiology meeting that compared three molecular C. difficile assays (one LAMP-based and two PCR-based) for performance. In this study, all three assays correlated very well. The conclusion was that all three molecular assays are acceptable alternatives to toxigenic culture for detecting toxigenic C. difficile directly from stool specimens.

Additionally, as we used the LAMP-based assay in our laboratory, we found that it was a very good alternative for the needs of our laboratory. The assay process was extremely simple, the hands-on time was two to three minutes per sample, the total turnaround time of the assay was less than 60 minutes on average, and with no capital equipment cost, the system is very cost-effective. Overall, this LAMP-based assay is a very accurate, easy-to-use, and viable alternative for molecular C. difficile testing.

I would hope that CAP TODAY, with its reputation for comprehensive coverage of all viable assay alternatives, would present this as an alternative in its discussion of molecular C. difficile assays. While PCR is a solid technology and is the basis for a number of high-quality assays, our facility as well as others have demonstrated that there are clearly other easy, fast, and affordable molecular alternatives.

Judy A. Daly, PhD
Professor of Pathology
University of Utah
Director, Microbiology Laboratories
Primary Children’s Medical Center
Intermountain Healthcare
Salt Lake City