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Fluorescent Antibody Titration for Antistreptolysin O (ASO) Antibodies

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

This test measures the level of antibodies in your blood that respond to a toxin produced by certain bacteria, often linked to strep throat or other streptococcal infections.

Quick summary

["Helps diagnose past or current strep infections and assesses immune response to streptococcal bacteria."]

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

Key facts at a glance

LOINC
24290-9
Short code
FLUAV Ab sp2 Titr Ser
Synonyms
FLUAV Ab sp2 Titr Ser
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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 the Purpose of This Test?

Doctors may order this test to confirm a streptococcal infection (such as strep throat) when other tests like rapid strep swabs are inconclusive. It also helps evaluate immune response after treatment or in chronic conditions like rheumatic fever.

How Is the Sample Collected?

A blood sample is drawn from a vein, usually in your arm, by a healthcare professional. You may feel a small pinch when the needle goes in, but the procedure is quick and typically painless afterward.

What Does a Positive Result Mean?

A positive result indicates the presence of ASO antibodies, suggesting exposure to streptococcal bacteria. This can confirm a past or recent infection, but it does not always indicate active symptoms.

When Might You Need Follow-Up?

If your doctor suspects recurrent infections or chronic conditions like rheumatic fever, they may recommend follow-up ASO tests to monitor antibody levels over time.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: ASO Antibodies and Infections

Short name

ASO Antibody Titer

Frequently asked questions

Why was this test ordered?
Your doctor may have ordered this test to investigate symptoms like sore throat, fever, or joint pain that could be linked to a strep infection. It can also help track treatment effectiveness or rule out complications like rheumatic fever.
What are the typical reference ranges?
Reference ranges vary by lab and may not be standardized. Your results will be interpreted in the context of your clinical symptoms and medical history.
How long does it take to get results?
Results are usually available within 24 to 48 hours, depending on lab processing times. Your doctor will contact you with the findings once they are ready.
  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