C. diff Testing
Reviewed
Also called: C. difficile toxin test, Clostridium difficile, Glutamate dehydrogenase test (GDH), C. difficile culture
C. diff testing checks a sample of your stool (poop) for signs of an infection with a bacteria called C. diff.
Specimen: stool (fresh loose or liquid sample)
Why this test may be ordered
- To find out if C. diff is causing diarrhea
- Watery diarrhea three or more times a day with no other known cause
- Symptoms plus a high risk, such as recent antibiotics, age 65 or older, or a recent health care facility stay
Preparation and collection
You don't need any special preparations for C. diff testing.
You will need to provide a fresh sample of loose or liquid stool for your test. If you are unable to return the container right away, you should refrigerate your sample until you're ready to deliver it.
There is no known risk to having C. diff testing.
Understanding results
Your provider will consider all your test results, your symptoms, and your medical history to figure out whether C. diff is causing your illness.
- Positive (abnormal) C. diff test: A positive (abnormal) test result may mean that toxins from C. diff bacteria are causing your symptoms. Limitation: GDH antigen tests can show if you have C. diff in your body. But they can't tell if it's making you sick. Next step: If you're diagnosed with a C. diff infection while you're taking an antibiotic for another infection, your provider may tell you to stop taking it. Your treatment may include: Taking a different type of antibiotic that targets C. diff bacteria, Fluids if you are dehydrated.
- Negative (normal) C. diff test: A negative (normal) test result generally means that no signs of a C. diff infection were found in your sample. Your symptoms are probably caused by something else. Limitation: But a negative result on a C. diff toxin test alone isn't enough to rule out a C. diff infection. That's because C. diff toxins can break down quickly if your sample isn't kept cool. Next step: If you have questions about your results and/or treatment, talk with your provider.
- Toxins can break down if the sample isn't kept cool, so a toxin test may miss an infection.
- GDH antigen tests can show C. diff is present but not whether it is making you sick.
- You usually won't be retested after treatment because C. diff often stays in the body.
What to do next
If you have questions about your results and/or treatment, talk with your provider.
- Which C. diff tests will be done on my sample?
- Should I keep taking my current antibiotic?
- How can I avoid spreading C. diff to others?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.