Stool C. difficile toxin

This test detects the presence of toxins produced by the bacterium Clostridium difficile (C. difficile) in the stool. C. difficile is a common cause of diarrhea after antibiotic use.

How the test is performed

A sample of a stool is submitted for laboratory analysis. There are several laboratory methods used to detect C. difficile toxin in the stool specimen. For many years, a cell cytotoxin assay has been used. This method incubates the stool specimen in the laboratory with tissue culture cells that are monitored over 24 to 48 hours for a specific reaction.

More recently, an enzyme immunoassay (EIA) to detect the toxins of C. difficile has been used. The EIA is faster, simpler to perform, and results are available in about an hour, but it is slightly less sensitive than the cell culture method.

How to prepare for the test

There are many ways to collect the samples. You can catch the stool on plastic wrap that is loosely placed over the toilet bowl and held in place by the toilet seat. Then put the sample in a clean container. One test kit supplies a special toilet tissue that you use to collect the sample, then put the sample in a clean container.

Do not mix urine, water, or toilet tissue with the sample.

For children wearing diapers, you can line the diaper with plastic wrap. If the plastic wrap is positioned properly, isolating the stool from any urine output, mixing of urine, and stool can be prevented for a better sample.

How the test will feel
There is no discomfort.

Why the test is performed
The test may be done when there is a suspicion that diarrhea is the result of recent antibiotic use. Antibiotics alter the bacterial flora in the colon and this sometimes results in excessive growth of C. difficile, whose toxins cause diarrhea. diarrhea caused by C. difficile following antibiotic use occurs frequently in hospitalized patients.

Normal Values

No C. difficile toxin detected.

What abnormal results mean

Abnormal results mean that C. difficile toxins are likely present in the stool and are causing diarrhea.

What the risks are

There are no risks associated with testing for C. difficile toxin.

Special considerations

Since the test for C. difficile toxin is not 100% sensitive, several stool samples may be needed to detect it.

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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