IgA Anti-Streptolysin O (ASO) Antibody, Serum
This test measures the level of antibodies in your blood that your immune system produces in response to certain bacteria, specifically *Streptococcus pyogenes* (group A streptococcus). It helps identify past or recent infection with these bacteria.
["This test helps doctors diagnose or monitor strep throat or other infections caused by group A strep bacteria."]
Key facts at a glance
- LOINC
- 49233-0
- Short code
- G lamblia+C parvum Ag Stl Ql Rapid
- Synonyms
- G lamblia+C parvum Ag Stl Ql Rapid
- Category
- coagulation
- Sample
- stool
- Container
- Clean container
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- rapid-less-than-minutes
- Specimen volume
- 5 g
- Stability
- Refrigerated: 24h, Frozen: 7d
- TAT
- 4–24 hours
- Order
- routine
What Does This Test Measure?
The IgA ASO test detects IgA antibodies against Streptolysin O, a toxin produced by group A streptococci. These antibodies develop after infection and can persist for months or years. The test is primarily qualitative, meaning it provides a yes/no result rather than a specific concentration.
Why Might You Need This Test?
Your healthcare provider may order this test if you have symptoms like sore throat, fever, rash, or joint pain that suggest strep throat or a post-strep complication (e.g., rheumatic fever). It’s also used to confirm a diagnosis when rapid strep tests are inconclusive or to monitor chronic infections.
How Is the Test Performed?
A blood sample is drawn from a vein in your arm. The serum (liquid part of blood) is then tested for IgA ASO antibodies using an immunoassay method, which detects the presence of these antibodies without measuring exact amounts.
What Are Possible Results?
A positive result indicates recent or past infection with group A strep bacteria. A negative result means no detectable antibodies were found, suggesting no current infection. Results are qualitative and interpreted by your doctor based on clinical symptoms and other factors.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A positive IgA ASO test is strongly associated with a history of group A strep infection, which can lead to complications like rheumatic fever or acute glomerulonephritis. While IgA antibodies are less commonly measured than IgG, they can still be useful in diagnosing delayed or chronic infections. Your doctor will use this result alongside symptoms, physical exam findings, and other tests to guide treatment or further evaluation.
Short name
IgA ASO Antibody
Frequently asked questions
What Does a Positive Result Mean?
What Does a Negative Result Mean?
How Long Do IgA ASO Antibodies Stay in the Blood?
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