Serum/Plasma Antistreptolysin O (ASLO) Antibody, Substance Concentration
This test measures the level of antibodies your body produces in response to a bacterial infection caused by *Streptococcus pyogenes* (group A streptococcus). It helps identify past or recent strep throat or other infections.
["ASLO helps diagnose strep infections and assesses immune response to bacterial exposure."]
Key facts at a glance
- LOINC
- 26975-3
- Short code
- ENA Scl70 Ab Ser IA-aCnc
- Synonyms
- ENA Scl70 Ab Ser IA-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- 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 ASLO Used For?
ASLO testing is primarily used to detect antibodies that develop after exposure to group A streptococcus bacteria. It can help confirm a diagnosis of strep throat (pharyngitis) when throat cultures or rapid strep tests are inconclusive. It may also be used in cases of rheumatic fever or other autoimmune conditions linked to prior strep infections.
How Is the Sample Collected?
A blood sample is drawn from a vein, usually in your arm. You may feel a small pinch when the needle is inserted, but the process is quick. The blood is then sent to a lab for analysis.
What Does a Positive ASLO Result Mean?
A positive ASLO result suggests your body has produced antibodies in response to a strep infection. This can indicate past exposure to group A streptococcus, such as from strep throat, scarlet fever, or other infections. However, a positive result alone doesn’t confirm the current infection—it only shows prior exposure.
When Might You Need This Test?
Your healthcare provider may order an ASLO test if you have symptoms like sore throat, fever, swollen lymph nodes, or rash that could suggest strep throat. It may also be used in cases of unexplained joint pain, skin rashes, or other symptoms linked to autoimmune reactions triggered by past strep infections.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
ASLO testing is valuable for diagnosing strep throat when rapid tests or cultures are negative. High levels of ASLO antibodies can also help monitor chronic conditions like rheumatic fever, where recurrent strep infections may have triggered autoimmune responses. However, ASLO is not a real-time test—it reflects past exposure, so it’s best used alongside other diagnostic tools for current infections.
Short name
ASLO Antibody
Frequently asked questions
Why might my ASLO test be ordered even if I don’t have symptoms?
Can ASLO test results change over time?
Is ASLO testing the same as a throat culture?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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