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Enzyme Immunoassay Methods

The most common laboratory tests for detection of C. difficile are enzyme immunoassays (EIA) for detection of C. difficile Toxin A and Toxin B. The immunoassays are simple to perform and provide rapid results. However the sensitivities of these tests are not as good as culture, CCNA, or molecular methods.

Only liquid stool samples should be processed. Due to the fact that the colonization rate is high, a positive result with a normal stool sample proves that the patient is colonized with C. difficile but not necessarily infected.

There are many test kits available commercially for detection of C. difficile toxins. Results are available in 15 minutes to 2 hours, depending on assay. Initially Toxin A was thought to be the toxin responsible for the majority of the effects of C.difficile disease. Therefore, most early test kits only detected Toxin A, based on monoclonal anti-Toxin A antibodies. With the discovery that there are strains that cause infection and produce aberrant or no Toxin A (A-), it is now recommended that a kit is used that detects both toxins.