Clostridioides difficile Toxin A and B (Qualitative) Assay
This test checks for toxins produced by the bacteria *Clostridioides difficile*, which can cause severe diarrhea and intestinal inflammation. It helps diagnose a condition called pseudomembranous colitis.
["This test helps determine if you have *Clostridioides difficile* infection, which can cause dangerous gut symptoms."]
Key facts at a glance
- LOINC
- 26697-3
- Short code
- CDIFFIGA
- Synonyms
- C diff IgA Ser-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or red-top tube without anticoagulant
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Enzyme Immunoassay (EIA)
- CPT
- 86677
- SNOMED
- 1089001000119102
- Specimen volume
- 0.5-1 mL serum
- Stability
- Serum stable for 7 days at 2-8°C; for longer storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you have symptoms like severe diarrhea, abdominal pain, or fever—especially if you’ve recently been in a healthcare setting or taken antibiotics. It’s also used to confirm a diagnosis of *Clostridioides difficile* infection in people with unexplained diarrhea or colitis.
What to Expect Before the Test
No special preparation is needed. You may provide a stool sample (usually collected at home) or a sample from your doctor’s office. If testing is done in a lab, your provider will guide you on how to collect it safely.
How the Test Works
The test detects the presence of toxins A and B from *Clostridioides difficile* using an immunoassay method. These toxins are responsible for causing gut damage and symptoms. The result tells whether the bacteria are producing these toxins in your stool.
Test Results and Interpretation
A positive result means your stool contains the toxins, strongly suggesting an active *Clostridioides difficile* infection. A negative result means the toxins were not detected, but other causes of diarrhea may still be possible. Your doctor will discuss the next steps based on your symptoms and test results.
Reference range
Reference ranges vary by laboratory and assay manufacturer; results should be interpreted in conjunction with clinical findings and other diagnostic tests such as stool toxin assays and PCR.N/A
No special patient preparation required. Sample may be collected at any time of day.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
C. diff Toxin Screen
Frequently asked questions
What does a positive result mean?
What does a negative result mean?
Can this test be done at home?
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 16, 2026. · Read our editorial policy