Skip to content

Antibody to Streptococcal Group A Bacteria (Serum) – Confirmatory Test

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

This test measures antibodies produced in response to certain bacterial infections, specifically Group A Streptococcus (e.g., strep throat or skin infections). It helps confirm past or active infection.

Quick summary

["This test helps diagnose strep infections by detecting antibodies your body makes after exposure to Group A strep bacteria."]

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

Key facts at a glance

LOINC
30150-7
Short code
ASO Ab sp2 Ser-aCnc
Synonyms
ASO Ab sp2 Ser-aCnc
Category
coagulation
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

Why This Test Is Done

Your doctor may order this test if you have symptoms like sore throat, fever, or skin rashes that could be caused by Group A strep bacteria. It’s also used to check if you have an ongoing infection or to confirm a previous one.

What to Expect Before the Test

No special preparation is needed. You’ll provide a blood sample drawn from your arm. The sample is sent to a lab for testing.

What the Test Results Mean

Positive results indicate your body has produced antibodies against Group A strep, suggesting past or recent infection. Negative results mean no detectable antibodies, so further testing or observation may be needed.

Common Causes of Positive Results

Positive results are most common in people who have had strep throat, scarlet fever, or other Group A strep infections. Rarely, it may appear in people with autoimmune conditions or other infections.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is critical for diagnosing Group A strep infections, guiding treatment decisions (such as antibiotics), and preventing complications like rheumatic fever. It’s not used to diagnose active infections in real-time but helps confirm past exposure or immune response.

Short name

ASO (Anti-Streptolysin O) Confirmatory

Frequently asked questions

What does a positive ASO test mean for my health?
A positive ASO test suggests your body has detected Group A strep bacteria at some point, but it doesn’t always mean you’re currently infected. It may indicate you had a strep infection earlier or could be at risk for complications like rheumatic fever if untreated.
How long does it take to get results from this test?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will discuss the results with you.
Can I take antibiotics before getting this test?
Yes, you can take antibiotics before testing, but it may affect the results. If you’re unsure, ask your doctor to clarify whether testing is still needed.
  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