The stool C. difficile toxin test detects harmful substances produced by the bacterium Clostridium difficile (C. difficile) in a stool sample. This infection is a common cause of diarrhea after antibiotic use.

A sample of a stool is submitted for laboratory analysis. There are several methods used to detect C. difficile toxin in the stool specimen.

Today, an enzyme immunoassay (EIA) is most often used to detect substances produced by the bacteria. The EIA is faster than previous culture tests, simpler to perform, and results are available in about an hour. However, it is slightly less sensitive than previous methods. Several stool samples may be needed to get an accurate result.

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 you put the sample in a clean container. One test kit supplies a special toilet tissue that you use to collect the sample. After collecting the sample, you put it in a 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, it will prevent urine and stool from mixing to provide a better sample.

There is no discomfort.

You may have this test if your doctor suspects that diarrhea is caused by recent antibiotic use. Antibiotics change the balance of bacteria in the colon. This sometimes leads to too much growth of C. difficile.

Diarrhea caused by C. difficile after antibiotic use often occurs in hospitalized patients. It also can occur in people who have not recently taken antibiotics.

No C. difficile toxin is detected.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

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

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

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

Bartlett JG. Clostridial infections. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 319.