Diphtheria Antigen Detection in Pharyngeal Swab (Qualitative Immunoassay)
This test checks for the presence of diphtheria bacteria in a throat swab using a sensitive antibody-based method.
["A positive result may indicate an infection requiring urgent medical attention."]
Key facts at a glance
- LOINC
- 105619-1
- Short code
- CDIPTH
- Synonyms
- C diphtheriae Throat Ql Cult
- Category
- chemistry
- Sample
- serum
- Container
- Sterile transport swab system (e.g., Amies or Stuart transport medium); dual swab recommended for optimal recovery
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- culture
- CPT
- 87081
- SNOMED
- 59751008
- Specimen volume
- Not applicable - quality of specimen (visible pseudomembrane material or exudate on swab) is more important than volume
- Stability
- Room temperature: deliver to laboratory within 2 hours of collection. If delayed, refrigerate at 2-8°C for up to 24 hours. Do not freeze.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–168 hours
- Order
- routine
Why This Test Is Done
Your doctor may order this test if you have symptoms like sore throat, fever, or difficulty breathing, especially if you’ve been exposed to someone with diphtheria. It helps confirm if the infection is severe enough to need treatment with antibiotics or antitoxin.
What to Expect During the Test
You’ll have a swab inserted gently into your throat to collect a sample. The swab is then sent to a lab for testing. The result is typically available within hours or a few days, depending on lab processing.
How the Test Works
The test detects specific proteins (antigens) from *Corynebacterium diphtheriae*, the bacteria that causes diphtheria. Antibodies in the test bind to these antigens if they’re present, triggering a visible reaction that confirms infection.
What the Results Mean
A **positive** result means diphtheria bacteria are likely present and may require immediate medical care. A **negative** result means no diphtheria was found in this sample, but other causes of symptoms should still be evaluated.
Reference range
Negative for Corynebacterium diphtheriae. Presence of toxigenic C. diphtheriae is considered clinically significant and reportable.N/A
Patient should not have eaten, drunk, or used mouthwash/gargle for at least 1 hour prior to collection. Avoid recent antibiotic therapy if possible, as it may reduce culture yield. Specimen should be collected before initiating antimicrobial therapy when clinically feasible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Diphtheria Swab Test (Qualitative)
Frequently asked questions
Diphtheria is a serious bacterial infection that can cause severe throat swelling, breathing difficulties, and even heart or nerve damage if untreated. Early detection with this test allows for prompt treatment with antibiotics or antitoxin to prevent complications.
If you’ve had recent exposure to someone with diphtheria, your doctor may recommend this test even if you don’t have symptoms. False negatives can occur if the sample isn’t collected properly or if the infection is very early.
This test is not the same as a blood test for diphtheria antibodies (e.g., *IgG* or *IgM*). It specifically looks for the bacteria itself in your throat.
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