C. diff Testing. Preparations and Results
C. difficile Testing
C. diff testing for a C. difficile infection, which is a serious disease of the digestive tract. What are the test types, preparations, and results?
Table of Contents
C. diff Testing – Clostridium difficile test is used to identify these bacteria and the toxin that causes diarrhea linked to antibiotic use. This test is important because it can help your doctor determine the best treatment for you.
Why do I need C. diff testing?
If you have been taking antibiotics and develop diarrhoea, it could be a sign of a C. diff infection. C. diff is short for Clostridium difficile, a type of bacteria that can cause severe diarrhoea and other problems in the gut.
C. diff infections can be difficult to treat and may lead to serious complications, so it is important to get tested if you think you may have one. Testing involves taking a sample of your stool (faeces) and sending it to a laboratory for analysis.
There are several different types of tests that can be used to detect C. diff, but the most important one is the toxin test. This test looks for toxins produced by the bacteria that are responsible for the symptoms of C. diff infection.
Accurate and timely diagnosis is critical because C. diff infections can worsen quickly and lead to serious complications such as dehydration, malnutrition and even death.
Other names: C. diff. culture, C. difficile toxin test, C. difficile, Glutamate dehydrogenase test GDH, Clostridium difficile, Clostridioides difficile.
What is the purpose of C. diff testing?
If you show any of the following symptoms, particularly if you’ve recently taken antibiotics, you may require C. diff testing:
- Watery diarrhoea that occurs three or more times per day and lasts for more than four days.
- Stool containing blood or mucus.
- Pain in the abdomen.
- Vomiting and nausea.
- Loss of weight.
- Appetite loss.
If you have these signs as well as certain risk factors, you are more likely to require C. difficile testing. You are more likely to get a C. diff infection if you:
- Are older than 65 years old.
- Are you a hospital patient.
- In a nursing home or other health care facility.
- Have inflammatory bowel disorder or any digestive disorder.
- Recently underwent gastrointestinal surgery.
- Undergoing cancer chemotherapy.
- Have immune system disease.
- Had previously been infected with C. diff.
How Is C. diff Diagnosed?
The following are part of the one-step procedure:
Toxin genes detected by C. difficile toxin gene testing using nucleic acid amplification tests (NAAT), which is typically a real time polymerase chain reaction (PCR). These are quick and sensitive methods for confirming the presence of the C. difficile toxin gene.
There is a multi-step procedure that includes:
- A test for a C. difficile antigen called glutamate dehydrogenase is used to perform an initial screen on stool samples (GDH). It is thought to be very sensitive, but it is not very specific for C. difficile toxin producers. This test detects the presence of C. difficile but not whether the bacteria are producing toxins.
- Positive screening results should be followed up with a test to confirm and detect the presence of toxins, using:
- Enzyme immuno assay (EIA) tests, which are quick but insensitive.
- Some times positive GDH test combined with a negative difficile toxin testing EIA results in an NAAT.
- It is recommended that a NAAT toxin gene test be followed by testing for toxigenic as an alternative multi-step procedure (rather than a NAAT test by itself).
Preparations for C. diff Testing
To prepare for the C. diff test, your doctor will likely ask you to stop taking any antibiotics that you are currently taking. You may also be asked to fast for a period of time before the test.
What happens during C. diff testing?
During the C. diff test, a specimen of unformed stool (liquid poo) will be collected and analyzed for the presence of C. diff bacteria and toxins.
Tests for C. diff toxins, bacteria, and/or genes that produce the toxins may be performed. However, all tests can be carried out on the same sample. Your healthcare provider will provide you with specific instructions for collecting your sample. You may include the following instructions:
- Wear rubber or latex gloves.
- Collect the loose stool and place it in a special sterile container provided by the lab.
- Make certain that there is no urine or toilet water in the sample.
- The container should be sealed and labelled.
- Remove your gloves and thoroughly wash your hands.
- Return the container to your doctor as soon as possible.
Toxins produced by C. diff may be more difficult to detect when stool is not tested quickly enough. If you can’t get to your provider right away, keep your sample refrigerated until you’re ready to deliver it.
What do the results mean?
If your C. diff test results are negative, it means that you probably do not have an infection with C. diff colitis. However, this test is not always accurate, so your doctor may order additional tests to be sure.
If your results are positive, it means that you have a toxin produced by C. diff bacteria in your stool sample.
This can cause severe symptoms, so it is important to see your doctor right away and start treatment.
Treatment Options for C. diff
The most common treatment options for C. diff are:
- Antibiotics such as metronidazole, fidaxomicin, and vancomycin, are usually taken for 10-14 days.
- Stop antibiotics that can kill good bacteria and make the infection worse.
- Taking probiotics, a kind of supplement. Probiotics are “good bacteria.”
The sample must be fresh for C. diff. toxin testing because the toxin degrades in one to two hours and can result in a false-negative test.