Anti-Streptolysin O Antibody (ASO) Test
The ASO test measures antibody levels against streptolysin O, a substance produced by group A streptococcal bacteria, in a blood sample. Quest describes it as a sensitive test for recent streptococcal infection.
About this test
Anti-streptolysin O, or ASO, is an antibody the immune system produces in response to streptolysin O, a substance released by group A streptococcal bacteria. Quest measures ASO levels in a 1 mL serum sample using an immunoturbidimetric method, and notes that levels rise after a streptococcal infection but do not rise with cutaneous, or skin, infections.
Quest describes elevated ASO levels as a common finding in people with acute rheumatic fever or acute glomerulonephritis following a streptococcal infection. After infection, ASO levels typically rise over the following weeks, peak some weeks after that, and, absent complications or reinfection, gradually return toward preinfection levels over the following months.
Who might consider this test?
- Because ASO reflects a systemic, not skin, infection, the clinical picture behind the request shapes how the result is read.
Test details
| Quest code | 265 |
|---|---|
| Methodology | Immunoturbidimetric |
| Sample type | 1 mL serum |
| Collection | Quest patient service center |
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Quest resources
Additional details
What this test looks at
The test reports a single value: the level of antibody to streptolysin O in blood serum. Quest lists it under several names, including Streptolysin-O Antibody, ASO, and Strep A, which all refer to the same measurement.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does the ASO test measure?
It measures the level of antibody to streptolysin O in a serum sample, using an immunoturbidimetric method.
How is the sample collected?
A 1 mL serum sample is collected during a routine blood draw.
Do I need to prepare for this test?
No preparation instructions are listed for this test, though people follow any instructions their ordering clinician provides.
Why might a clinician order this test?
Quest describes ASO as a sensitive test for recent streptococcal infection, with elevated levels a common finding in people with acute rheumatic fever or acute glomerulonephritis.
Does ASO rise with skin infections?
No. Quest notes that ASO levels rise after streptococcal infection but do not rise with cutaneous (skin) infections.
Can I get the Anti-Streptolysin O Antibody test without a doctor's visit or insurance?
Yes. The $60 cash price includes an independent physician's order, so no referral is needed, and insurance is never involved.