IgA Antibody to Streptococcal Group A (Anti-Streptolysin O, ASO) in Serum/Plasma
This test measures antibodies produced in response to certain bacterial infections caused by Group A Streptococcus, such as strep throat or skin infections.
["Helps diagnose past or recent strep infections and assesses immune response to the bacteria."]
Key facts at a glance
- LOINC
- 1005-8
- Short code
- IAT IgG-Sp Reag SerPl Ql
- Synonyms
- IAT IgG-Sp Reag SerPl Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82784
- 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 Is This Test Measuring?
The test detects **anti-streptolysin O (ASO) antibodies**, which the immune system creates in reaction to the streptococcal enzyme streptolysin O. This enzyme is released when the bacteria invade your body. Elevated levels may indicate a history of Group A strep infection, even if symptoms have resolved.
Why Might Your Doctor Order This Test?
Your doctor may recommend this test if you’ve had symptoms like sore throat, fever, or skin rashes that could suggest Group A strep infection, or if you’ve been exposed to the bacteria. It’s also used to monitor chronic conditions like rheumatic fever, which can develop after untreated strep infections.
What Does a Positive Result Mean?
A positive result (higher-than-normal antibody levels) suggests you’ve had a recent or past Group A strep infection. However, it doesn’t always mean you’re currently infected—some people may have lingering antibodies for months or years. False positives can occur in rare cases, so results should be interpreted by a healthcare provider.
What to Expect During the Test
You’ll have a small needle inserted into your arm to draw blood. The sample is sent to a lab for analysis. The test typically takes 1–3 days to return results, depending on lab processing times.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
ASO antibodies are important for diagnosing strep infections, particularly in cases where throat cultures or rapid antigen tests are inconclusive. They’re also used to track complications like rheumatic fever, which can develop weeks or months after untreated strep infections. However, ASO levels alone shouldn’t replace other diagnostic tools like cultures or clinical judgment.
Short name
Anti-Streptolysin O (ASO) Test
Frequently asked questions
How long does it take to get results from this test?
Can I eat or drink before this test?
What if my ASO test is positive but I don’t remember having a strep infection?
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