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Serum or Plasma Immunoassay for Anti-Streptococcal Antibodies (Group A Streptococcus, ASOT)

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

This test measures your immune system’s response to Group A Streptococcus bacteria, which can cause infections like strep throat or skin infections.

Quick summary

["Helps identify past or current strep infections by detecting antibodies your body produces."]

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

Key facts at a glance

LOINC
10087-5
Short code
ST I-Amp 6ms L-III
Synonyms
ST I-Amp 6ms L-III
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ekg
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 This Test Measures

The test looks for antibodies (specifically anti-streptolysin O, or ASO) produced in response to Group A Streptococcus bacteria. These antibodies are a sign your immune system has encountered the bacteria, often following an infection like strep throat or scarlet fever.

Why It’s Ordered

Your healthcare provider may order this test if you have symptoms of a recent strep infection (e.g., sore throat, fever, red rash) or if you’ve been exposed to someone with a strep infection. It can also help confirm a diagnosis when other tests are inconclusive or if you have recurrent infections.

Sample Collection and Preparation

A blood sample is taken from a vein in your arm. The blood is processed to separate the serum or plasma, which is then tested for ASO antibodies using an immunoassay method. This method detects the presence and level of antibodies without needing to culture the bacteria.

What to Expect Before the Test

No special preparation is needed. You may have some mild discomfort from the needle, but it usually goes away quickly. If you’re on blood-thinning medication, let your provider know before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ASOT Antibody Test

Frequently asked questions

How long does it take to get results?
Results are typically available within 1 to 3 business days, depending on your lab’s processing time.
Can I have a false positive or negative result?
Yes, false results can occur. False negatives may happen if the infection was very recent or resolved quickly. False positives can result from other infections, autoimmune conditions, or rare cross-reactions. Your provider will discuss results in context with your symptoms and medical history.
Does this test replace a throat culture?
No, this test is not a direct culture. While it can help identify a past or current strep infection by detecting antibodies, a throat culture is the gold standard for confirming active strep throat. Your provider may use both tests together for accurate diagnosis.
  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