ASO Titre (Anti-Streptolysin O)
A blood test that shows a recent strep infection, used when rheumatic fever is suspected.
Quick Summary
To support a diagnosis of rheumatic fever or post-strep kidney disease.
Antibodies to streptolysin O.
No preparation needed.
Overview
Levels rise a few weeks after a strep throat infection.
It doesn't diagnose current sore throat; a throat swab does.
What It Measures
ASO titre
Antibody level.
How It's Performed
- 01
Preparation
Usually no special preparation. Tell the staff about medicines you take.
- 02
Blood sample
A small amount of blood is taken from a vein in your arm with a thin needle.
- 03
Afterwards
Press on the spot for a minute. A small bruise is common; you can go back to normal activities.
Reference Ranges
Note: Normal ranges vary by laboratory. Consult your report for the specific reference used.
| Parameter | Typical Range (Adult) | Units |
|---|---|---|
| ASO (adults) | Below 200 | IU/mL |
Interpreting Results & Next Steps
Discuss with Doctor
Children often have higher levels. Normal ranges differ between laboratories, ages and sexes; always use the range printed on your report and ask your doctor what your results mean.
If values are High:
A high or rising titre suggests recent strep infection.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Strep A Test(opens in a new tab) · MedlinePlus, US National Library of Medicine