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Anti-Streptolysin O Antibody, Serum (ASO) - Quantitative

Published: August 9, 2026Updated: August 16, 2026

This test measures the level of antibodies your body produces in response to a bacterial toxin called Streptolysin O, often found in group A Streptococcus infections.

Quick summary

["Helps diagnose or monitor strep throat or other streptococcal infections."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
25788-1
Short code
ASO Ab Ser LA-aCnc
Synonyms
ASO Ab Ser LA-aCnc
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
la
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

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms like sore throat, fever, swollen lymph nodes, or rash, especially if strep throat is suspected. It can also be used to check for recurrent infections or evaluate heart or joint damage caused by untreated strep infections.

What to Expect Before the Test

No special preparation is needed. You may have a blood sample drawn from a vein in your arm, usually at a lab or your doctor’s office. The process is quick and typically causes only mild discomfort.

What the Test Results Mean

Higher levels of ASO antibodies suggest recent or ongoing streptococcal infection. Results alone don’t confirm the diagnosis but can support it when combined with symptoms and other tests.

Common Causes and Conditions

Elevated ASO levels are most commonly linked to group A Streptococcus infections (e.g., strep throat, scarlet fever). Rarely, it may appear in other bacterial infections or autoimmune conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ASO Antibody

Frequently asked questions

How long does it take to get results from this test?
Results are usually available within 1–3 business days, depending on your lab’s processing time. Your healthcare provider will discuss the findings with you.
Can I take antibiotics before getting this test?
Yes, if you’re prescribed antibiotics for suspected strep infection, take them as directed. However, your provider may need to retest after treatment to confirm the infection is cleared.
Does this test detect all types of strep infections?
No, it specifically measures antibodies to Streptolysin O, which is produced by group A Streptococcus. Other strep types (e.g., group B) won’t be detected by this test alone.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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