At a glance
Also known as
ASOT; ASO; Streptococcal serology
Why get tested?
To help determine whether a person has had a recent Group A streptococcal infection; to help diagnose post-streptococcal of and glomerulonephritis
When to get tested?
When someone has a fever, chest pain, fatigue, shortness of breath, , or other symptoms associated with rheumatic fever or glomerulonephritis, especially when a person recently had a sore throat but no culture was done to confirm a Group A streptococcal infection
A blood sample drawn from a vein in your arm
Test preparation needed?
What is being tested?
This test measures the amount of antistreptolysin O (ASO) in the blood. ASO is an targeted against streptolysin O, a toxin produced by Group A streptococcus (Streptococcus pyogenes). Streptolysin O, is an oxygen-sensitive protein which bursts open red blood cells so the bacterium can get access to nutrients and increase in numbers. ASO and anti-DNase B are the most common of several antibodies that are produced by the body's immune system in response to a Group A streptococcal infection.
Group A streptococcus, is the bacterium responsible for causing most strep throat infections. When strep infections are identified and, treated with antibiotics, the infection should resolve. However, when a strep infection does not cause identifiable symptoms and, goes untreated, or is treated with ineffective antibiotics, post-streptococcal complications () may develop. These are more common in young children and include, and glomerulonephritis. There has been a worldwide reduction in diseases caused by Group A Strep, but infections still occur. In Australia, the Indigenous population is disproportionately affected by these diseases. Group A streptococcus infections may cause symptoms such as fever, fatigue, shortness of breath, heart palpitations, decreased urine output, and bloody urine. They can damage the heart and/or cause acute kidney dysfunction, leg swelling (), and high blood pressure (hypertension). Because these symptoms may also be seen with other conditions, the ASO test can be used to help determine if they are due to a recent Group A strep infection.
For more information on rheumatic fever and glomerulonephritis, see the Related Links tab.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.