Does this test have other names?

C. diff, C. difficile

What is this test?

This is a test to look at your bowel movement (stool) for harmful substances called toxins produced by Clostridioides (formerly 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 become overgrown. 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, especially 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?

You may need this test if you have any of these symptoms, especially if you are in the hospital or were recently taking antibiotics:

• Diarrhea. This means 3 or more loose stools per day for at least 2 days.

• Blood or mucus in your stool

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

What other tests might I have along with this test?

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

If your stool tests are negative, but your healthcare provider still strongly suspects C. difficile infection, you may have a sigmoidoscopy or colonoscopy to help make a diagnosis. In this procedure, a healthcare provider 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 healthcare providers are likely to test people in this group who develop persistent diarrhea after taking antibiotics.

What do my test results mean?

Test results may vary depending on your age, gender, health history, the method used for the test, and other things. Your test results may not mean you have a problem. Ask your healthcare provider what your test results mean for you. 

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 healthcare provider still suspects infection, they may do other tests.

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

How is this test done?

This test needs a stool sample. Your healthcare provider will direct you how to collect a sample into a disposable specimen container with a lid. Do not collect stool 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 affect the results.

How do I get ready for this test?

You don't need to prepare for this test. Be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.