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Clostridium Difficile Toxin Stool Test

Last updated Sept. 24, 2018

Approved by: Krish Tangella MD, MBA, FCAP

The Clostridium Difficile Toxin Stool Test for C. difficile detects the presence of an infection, by analyzing stool samples.

What are the other Names for this Test? (Equivalent Terms)

  • C. Diff Toxin Stool Test
  • C. Difficile Toxin Stool Test
  • Glutamate Dehydrogenase Stool Test

What is Clostridium Difficile Toxin Stool Test? (Background Information)

  • Clostridium difficile is a bacterium that maybe present in the digestive tract, of about 65% of the healthy infants and 3% of healthy adults. They co-exist with other bacteria in the alimentary tract and remain in a balanced state
  • In some individuals, following a treatment with antibiotics, this balance of the gut flora (the complex group of microorganisms in the digestive tract) is disrupted, leading to an overgrowth of C. difficile
  • Some strains of these bacteria produce toxins A and B, which can damage the lower part of the bowel (colon), leading onto watery stools, abdominal pain, fever, and dehydration
  • The dead cells, some protein, and white blood cells, form, what is termed as a “pseudomembrane” over the colon. This is labeled as pseudomembranous colitis. In severe cases, the bowel may also get perforated or necrosed (necrosis is the death of cells)
  • Clostridium difficile infection is the most common cause of diarrhea in hospitalized patients. It may occur even weeks after completion of an antibiotic course, or following chemotherapy

The Clostridium Difficile Toxin Stool Test for C. difficile detects the presence of an infection, by analyzing stool samples. The tests that maybe performed on the stool samples include:

  • Enzyme immunoassay (EIA): A rapid test to look for the presence of toxins in stool. Although, results may be obtained within 1-4 hours, the test is not sensitive enough to detect infection in all cases
  • Glutamate dehydrogenase (GDH) test: This helps in detecting a C. diff infection; but, it cannot differentiate between the strains that produce and those that do not produce the toxins
  • Tissue culture: It takes about 24-48 hours to perform, and it looks for the effects of the toxins on cultured human cells
  • Polymerase chain reaction (PCR): A technique of producing increased copies of a particular DNA sequence and detecting the same in a sample. This helps to find the presence of C. diff toxin B gene (tcdB) in the stool specimen
  • Toxigenic stool culture: Bacteria in the specimen are grown in a culture and the toxins are detected. This is the most sensitive test (capable of identifying the diseased individuals correctly); though, the slowest tests, takes about 2-3 days, in order to obtain the results

Currently, a two-step testing process is recommended by the Infectious Diseases Society of America (IDSA) and the Society for Healthcare Epidemiology of America (SHEA). These are outlined below:

  • Perform the GDH (glutamate dehydrogenase) test first, to screen for Clostridium difficile
  • A positive GDH sample is further tested for the toxin, or the gene coding of the toxin

What are the Clinical Indications for performing the Clostridium Difficile Toxin Stool Test?

Indications for Clostridium Difficile Toxin Stool Test include symptoms, such as watery stools, crampy abdominal pain, fever, and nausea, in the following cases:

  • Individuals (especially hospitalized individuals), currently on antibiotics, or within 6-8 weeks of taking antibiotics, or following a chemotherapy or a gastrointestinal surgery
  • Individuals, with a known chronic digestive tract disorder, with worsening of symptoms
  • When no other cause for diarrhea, has been established
  • Individuals, who have previously been treated for Clostridium difficile - to check for any relapse

How is the Specimen Collected for Clostridium Difficile Toxin Stool Test?

Sample required: Stool


  • An unformed stool sample is collected in a sterile container for testing, without any contamination with urine or water
  • This has to be transported to the lab immediately, or refrigerated in case of a delay, as the C. diff toxin breaks down within 2 hours, at room temperature

Preparation required: None

What is the Significance of the Clostridium Difficile Toxin Stool Test Result?

A Clostridium Difficile Toxin Stool Test result may be positive or negative.

  • A positive test result indicates infection with toxin producing C. difficile, which requires treatment with appropriate oral antibiotics
  • A negative test result indicates diarrhea, due to other causes
  • Any improper collection/storage/transport of stool sample, may also give false negative test results; hence, the test may have to be repeated in such instances

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • A gastroenterologist may also examine the colon endoscopically and biopsy any pseudomembranes present, in order to diagnose Clostridium difficile colitis

The following article link will help you understand Clostridium difficile colitis.


Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: March 2, 2014
Last updated: Sept. 24, 2018