Tests and diagnosisBy Mayo Clinic staff
Doctors often suspect C. difficile in anyone with diarrhea who has recently taken antibiotics or when diarrhea develops a few days after hospitalization. In such cases, you're likely to have one or more of the following tests.
Toxins produced by C. difficile bacteria can usually be detected in a sample of your stool. Several main types of lab tests exist, and they include:
- Enzyme immunoassay. Most labs use the enzyme immunoassay (EIA) test, which is faster than other tests, but isn't sensitive enough to detect many infections and has a higher rate of falsely normal tests.
- Polymerase chain reaction. This sensitive molecular test can rapidly detect the C. difficile toxin B gene in a stool sample and is highly accurate. It's now being adapted by several laboratories and becoming more widely available.
- Cell cytotoxicity assay. A cytotoxicity test looks for the effects of the C. difficile toxin on human cells grown in a culture. This type of test is sensitive, but it is less widely available, more cumbersome to do and requires more than 24 to 48 hours for test results. Some hospitals use both the EIA test and cell cytotoxicity assay to ensure accurate results.
Testing for C. difficile is unnecessary if you're not having diarrhea or watery stools.
In rare instances, to help confirm a diagnosis of C. difficile infection, your doctor may examine the inside of your colon. This test (flexible sigmoidoscopy or colonoscopy) involves inserting a flexible tube with a small camera on one end into your colon to look for areas of inflammation and pseudomembranes.
If your doctor is concerned about possible complications of C. difficile, he or she may order an abdominal X-ray or a computerized tomography (CT) scan, which provides images of your colon. The scan can detect the presence of complications such as thickening of the colon wall, expanding of the bowel, or more rarely, a hole (perforation) in the lining of your colon.
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