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Clostridium Difficile Toxin (Stool)

Does this test have other names?

C. diff, C. difficile

What is this test?

This is a test to look at your stool for toxins produced by Clostridium difficile bacteria.

Your gastrointestinal (GI) tract is home to many healthy bacteria, and sometimes C. difficile is one of them. But in some cases, taking broad-spectrum antibiotics can upset the balance of healthy bacteria in your gut and cause new or antibiotic-resistant strains of C. difficile to grow out of control. These germs can then release toxins into your GI tract, inflaming the colon and causing continuing diarrhea. The resulting illness can be serious, even life-threatening, if you have a weak immune system.

Even if they are not taking antibiotics, people with a weak immune system often have an overabundance of C. difficile bacteria. 

Why do I need this test?

Your doctor might order this test if you have any of these symptoms, especially if you are in the hospital or were recently taking antibiotics:

  • Diarrhea that lasts longer than a few days

  • Persistent watery diarrhea

  • Blood or mucus in your stool

  • Stomach pain, nausea, or fever, particularly if you have persistent diarrhea 

What other tests might I have along with this test?

Your doctor might order other stool tests to look for C. difficile infection, such as a glutamate dehydrogenase, or GDH, test and a stool culture test.

If your stool tests are negative, but your doctor still strongly suspects C. difficile infection, you may have a sigmoidoscopy or colonoscopy to help make a diagnosis. In this procedure, a doctor examines your colon with a very thin, flexible lighted tube that is equipped with a tiny video camera on the end.

This infection is a major cause of illness and death among older adults who are in the hospital, so doctors are likely to test people in this group who develop persistent diarrhea after taking antibiotics. 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

A normal result for this stool test is negative, which means you had no C. difficile toxins in your sample. But this test result is not accurate all of the time. A small portion of people might have the infection even if the result is negative. If your doctor still suspects infection, he or she may do other tests.

If your stool tests positive for C. difficile toxins, your doctor may decide that you have antibiotic-associated colitis, or inflammation of the colon. 

How is this test done?

This test requires a stool sample. Your doctor will instruct you how to collect a sample into a disposable specimen container with a lid. Do not collect fecal material from the toilet bowl or put toilet paper into the specimen container.

Does this test pose any risks?

This test poses no known risks.

What might affect my test results?

Contaminating the stool sample with toilet water, urine, or other substances can make it unfit for testing or skew the results.

How do I get ready for this test?

You don't need to prepare for this test.