Clostridium difficile Toxin A and B Screening (Stool)
This test checks for toxins produced by *Clostridium difficile* bacteria, which can cause severe diarrhea and intestinal inflammation. It’s used to diagnose a condition called pseudomembranous colitis.
["A positive result may mean you have C. diff infection and need treatment."]
Key facts at a glance
- LOINC
- 20762-1
- Short code
- CDIFCULT
- Synonyms
- C diff Stl Ql Aerobe Cult
- Category
- chemistry
- Sample
- stool
- Container
- Sterile, wide-mouth, leak-proof container without preservative; anaerobic transport medium is preferred if culture is specifically requested. Cary-Blair or similar transport medium acceptable.
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- aerobic-culture
- CPT
- 87081
- SNOMED
- 409086009
- Specimen volume
- Minimum 1-2 mL or 1-2 grams of stool; 5-10 mL/grams preferred for adequate culture yield
- Stability
- Refrigerated (2-8°C): up to 48-72 hours. Room temperature: process within 2 hours of collection. Frozen: not recommended for culture. For delayed processing, transport in appropriate preservation medium.
- TAT
- 48–120 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you have symptoms like severe diarrhea (watery or bloody), abdominal pain, or fever after recent antibiotic use. It’s also used in hospital settings to check for infection in patients who’ve been exposed to C. diff.
What to Expect Before the Test
No special preparation is needed. Bring any medications you’re taking, as some antibiotics can increase your risk of C. diff infection. Avoid eating or drinking for a few hours before testing if instructed.
How the Test Works
A small stool sample is collected (usually via a swab) and tested for specific toxins (A and B) that *Clostridium difficile* releases. The test detects these toxins even if the bacteria aren’t visible under a microscope.
Possible Results and Next Steps
A negative result means no toxins were found, but symptoms may still be due to other causes. A positive result suggests C. diff infection and may lead to further testing or treatment with antibiotics (like vancomycin or fidaxomicin) and lifestyle changes (e.g., probiotics).
Reference range
Negative for Clostridioides difficile. No growth of toxigenic C. difficile isolated. Report as 'Not Detected' or 'No C. difficile isolated' for aerobic culture.N/A
No special patient preparation is required. If possible, specimen should be collected prior to initiation of antibiotic therapy (including metronidazole or vancomycin). Avoid contamination with urine or toilet water. Specimen should be collected from patients with diarrhea (unformed stool) rather than formed stool whenever possible, as C. difficile testing has higher yield in symptomatic patients.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
C. diff toxins cause inflammation in the colon, leading to severe diarrhea, dehydration, and complications like bowel obstruction. Early detection helps prevent complications and ensures proper treatment. Misdiagnosis can delay care, so follow-up with your doctor if symptoms persist or worsen.
Short name
C. diff Toxin Screen
Frequently asked questions
Will this test show if I have C. diff without symptoms?
How long does it take to get results?
Can I take probiotics before or after this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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