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Clostridium difficile Toxin A and B (Qualitative) in Stool

Published: August 9, 2026Updated: August 15, 2026

This test detects the presence of toxins produced by the bacteria *Clostridium difficile*, which can cause severe diarrhea and intestinal inflammation. It helps doctors diagnose pseudomembranous colitis or severe diarrhea linked to this infection.

Quick summary

["This test helps determine if your symptoms may be caused by a *Clostridium difficile* infection, which can be dangerous if untreated."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 15, 2026Editorial policy

Key facts at a glance

LOINC
6362-8
Short code
CDIF
Synonyms
C diff Tox A+B Stl Ql CT Tiss Cult
Category
chemistry
Sample
stool
Container
Sterile, leak-proof, wide-mouth container without preservatives; sterile screw-capped container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
cytotoxin-tissue-culture-assay
CPT
87230
SNOMED
41754007
Specimen volume
5-10 mL liquid stool or 5-10 g of semi-solid stool; minimum 1 mL for liquid specimens
Stability
Refrigerated (2-8°C): up to 72 hours. Frozen (-20°C or lower): up to 1 week. Room temperature: not recommended; process within 2 hours of collection. Avoid repeated freeze-thaw cycles.
TAT
48–96 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have symptoms like severe diarrhea (often with blood), abdominal pain, or fever after recent antibiotic use. It’s also used in hospital settings to check for infection in patients with unexplained diarrhea or colitis.

What to Expect Before the Test

No special preparation is needed, but you may be asked to collect a fresh stool sample in a sterile container. If you’re in a hospital, staff will guide you through the process.

How the Test Works

The test uses an immunoassay (often a chemiluminescent or fluorescence-based method) to detect toxin A and B in your stool. These toxins are proteins that *Clostridium difficile* releases to harm your intestines.

What the Results Mean

A positive result means toxins are present, strongly suggesting a *Clostridium difficile* infection. A negative result means no toxins were found, but other causes of diarrhea or colitis could still be possible.

Reference range

Negative: Toxin A and/or Toxin B not detected. Positive: Toxin A and/or Toxin B detected, indicating active Clostridioides difficile infection.N/A

Specimen: stool

No fasting required. Patient should avoid taking stool softeners, bismuth-containing preparations, barium, or antibiotics prior to collection if possible, as they may interfere with test results. Sample should be collected from the first loose or watery stool of the day if symptoms are present.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Positive results prompt immediate treatment with antibiotics (like vancomycin or fidaxomicin) and sometimes changes to your diet or bowel management. Untreated infections can lead to severe complications, including bowel damage or toxic megacolon. Early diagnosis is key to preventing complications.

Short name

C. diff Toxin Screen

Frequently asked questions

What does a positive result mean for my treatment?
A positive result means you likely have a *Clostridium difficile* infection. Your doctor will prescribe antibiotics (such as vancomycin or fidaxomicin) to kill the bacteria. They may also recommend changes to your diet or fluids to help your intestines heal. Follow their instructions carefully.
Can I still eat or drink normally while waiting for results?
Yes, you can continue eating and drinking normally unless your doctor advises otherwise. Avoid unnecessary antibiotics unless prescribed by your provider, as they can worsen *Clostridium difficile* infections.
Will I need to take any special precautions if my test is positive?
If your test is positive, your doctor may recommend avoiding certain foods (like dairy) or liquids that can irritate your intestines. You may also need to stay hydrated and avoid spreading the infection to others by practicing good hand hygiene.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 15, 2026. · Read our editorial policy