Fluorescent Immunoassay for Antistreptolysin O Antibodies (ASO) in Serum
This test measures the presence of antibodies your body makes in response to a bacterial infection caused by *Streptococcus* (group A). These antibodies help your immune system fight off the infection.
["ASO tests help diagnose recent strep throat or other strep infections."]
Key facts at a glance
- LOINC
- 59423-4
- Short code
- FLUAV HA RNA Spec NAA+probe
- Synonyms
- FLUAV HA RNA Spec NAA+probe
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- probe-amp-tar
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
The ASO test detects antibodies called antistreptolysin O (ASO) produced by your immune system after exposure to *Streptococcus pyogenes* (group A streptococcus). These antibodies are a sign that your body has responded to a bacterial infection, often linked to strep throat, scarlet fever, or other strep-related illnesses.
Why Might Your Doctor Order This Test?
Your doctor may recommend this test if you have symptoms like sore throat, fever, or rash that suggest strep infection, especially if antibiotics aren’t working as expected. It can also help confirm a diagnosis when other tests are inconclusive or if you’ve had symptoms for a few weeks.
How Is the Test Performed?
A blood sample is taken from a vein in your arm. The blood is then sent to a lab where it’s analyzed using a fluorescent immunoassay method to detect ASO antibodies.
What Are the Possible Results?
Results are qualitative (positive or negative) and indicate whether ASO antibodies are present. A positive result suggests recent strep infection, while a negative result means no detectable antibodies were found.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
ASO antibodies are useful for diagnosing strep infections, especially when symptoms persist or when other tests are unavailable. High levels may also indicate chronic strep infections or complications like rheumatic fever, though they can take weeks to develop after infection. Always discuss results with your healthcare provider.
Short name
ASO Antibody Test
Frequently asked questions
How long does it take to get results from this test?
Can I take anything special before this test?
Is this test safe?
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