Understanding Anti-Streptolysin O (ASO) Reference Range
Learn about the normal ASO range, its significance, and when to consult a doctor.
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is below the typical adult range (0–200 IU/mL).
is within the typical adult range (0–200 IU/mL).
is above the typical adult range (0–200 IU/mL).
This number is very far from the usual range - check which unit your report uses.
A value this far outside the range is worth discussing with your doctor today.
What a low result usually means
What a high result usually means
The range printed on your own report comes first - it differs between laboratories. This is not a diagnosis.
See it next to the rest of your report - upload it for a free, private explanationFree. Sign up with your email - no password, we send you a code.Anti-streptolysin O (ASO) is a blood test that measures the presence of antibodies against streptolysin O, a substance produced by group A Streptococcus bacteria. Understanding your ASO levels can help identify recent streptococcal infections, which are important for diagnosing conditions like rheumatic fever and post-streptococcal glomerulonephritis.
What is Anti-streptolysin O (ASO)?
ASO is an antibody that your body produces in response to an infection by group A Streptococcus bacteria. These bacteria can cause a variety of illnesses, including strep throat and skin infections. The ASO test detects these antibodies in your blood, providing evidence of a recent streptococcal infection.
Why the ASO Test Matters
The ASO test is crucial for diagnosing complications that can arise from streptococcal infections, such as rheumatic fever and post-streptococcal glomerulonephritis (a type of kidney inflammation). While the test does not diagnose an active sore throat, a raised or rising ASO level can indicate a recent infection and help support a diagnosis of these conditions.
Normal ASO Reference Range
For adults, the typical ASO reference range is 0 to 200 IU/mL. Clinically, an ASO level is typically considered normal if it is less than 200 IU/mL. A level above this range might suggest a recent group A streptococcal infection, which is significant for diagnosing related complications, rather than the infection itself.
Factors Affecting ASO Levels
Several factors can influence ASO levels. These include the timing of the test relative to the infection, as ASO levels may rise 1-3 weeks after the onset of infection and peak around 3-5 weeks. Additionally, not everyone will have elevated ASO levels after a streptococcal infection, as individual immune responses vary.
Frequently asked questions
What does a high ASO level mean? A high ASO level, typically above 200 IU/mL, suggests a recent group A streptococcal infection. It is used to support a diagnosis of conditions like rheumatic fever or post-streptococcal glomerulonephritis.
Can ASO levels be used to diagnose strep throat? No, ASO levels are not used to diagnose an active strep throat. They are used to identify recent infections that might lead to complications.
How long do ASO levels stay elevated? ASO levels can remain elevated for several months after an infection, gradually decreasing over time.
Do normal ASO levels rule out a past streptococcal infection? Not necessarily. Some people may not produce high levels of ASO antibodies even after a streptococcal infection.
When to see a doctor
You should consider seeing a doctor if you have symptoms of a streptococcal infection, such as a sore throat or skin rash, and are concerned about complications like rheumatic fever. If your ASO levels are elevated, your doctor can help determine the significance and whether additional tests or treatments are needed.
Remember, this information is for educational purposes and should not replace professional medical advice. Always consult with your healthcare provider for decisions regarding your health.