Skip to content

Fluorescent Antibody Assay for Antistreptolysin O (ASO) Antibodies

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

This test measures the presence of antibodies in your blood that develop in response to certain bacterial infections, such as strep throat caused by Group A Streptococcus.

Quick summary

["Helps diagnose recent strep infections and guides treatment decisions."]

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

Key facts at a glance

LOINC
15444-3
Short code
FLUAV Ab Ser Ql ID
Synonyms
FLUAV Ab Ser Ql ID
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
immune-diffusion
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 Used For?

Doctors may order this test if you’ve recently had symptoms like sore throat, fever, or rash that could suggest a Group A Streptococcus (strep) infection. It helps confirm whether the infection was bacterial rather than viral.

How Is the Sample Collected?

A small blood sample is drawn from a vein in your arm by a healthcare professional. The blood is then processed to detect specific antibodies linked to strep infections.

What Does a Positive Result Mean?

A positive result indicates your immune system has produced ASO antibodies, suggesting you likely had a strep infection within the past few weeks. This can help guide treatment with antibiotics.

What If My Result Is Negative?

A negative result means your body did not produce detectable ASO antibodies at the time of testing, which may indicate the infection was viral or resolved without bacterial involvement.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: This test plays a key role in diagnosing Group A Streptococcus infections, particularly in cases where symptoms like fever, rash, or persistent sore throat are present. It helps differentiate bacterial from viral causes and supports appropriate antibiotic treatment decisions.

Short name

ASO Antibody Test

Frequently asked questions

Why might my doctor request this test?
Your doctor may order it if you’ve had symptoms like a high fever, red throat, or rash that could signal a strep infection, especially if other tests (like rapid strep swabs) were negative or inconclusive.
Could false positives or negatives occur?
Yes, rare false positives may occur if you’ve had a previous strep infection or other infections. False negatives are less common but can happen if the test is taken too early after infection. Follow-up testing may be needed if symptoms persist.
How soon after infection might I get a positive result?
ASO antibodies typically appear within 1–3 weeks after a strep infection and remain detectable for several months. Results may take a few days to process, so discuss timing with your healthcare provider.
  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