Quick answer
The Anti-Streptolysin O (ASO) Test costs ₹270 at Live Line Health Care. Shows whether there has been a recent streptococcal infection, used when rheumatic fever or post-infection kidney inflammation is suspected weeks after a sore throat. No fasting is needed. It uses a blood sample and the report is usually ready the same day.
Also known as: ASO Titre, ASO Titer, Antistreptolysin O, ASLO, Anti Streptolysin O Titre, Strep Antibody Test, Rheumatic Fever Test
What is the ASO Test?
The ASO test measures antibodies against streptolysin O, a toxin made by group A streptococcus, the bacterium behind strep throat and some skin infections such as impetigo. The body starts making these antibodies about a week after the infection, and they peak around 3 to 5 weeks later before slowly falling over several months. So the ASO titre looks back in time: it shows whether a strep infection happened recently, even after the sore throat has cleared.
That backward view is exactly why doctors use it. Rheumatic fever, which can damage heart valves, and post-streptococcal glomerulonephritis, a kidney inflammation, appear weeks after an untreated strep infection, when throat swabs are often negative. Rheumatic heart disease is still seen in India, so the test is common in children and young adults with joint pain and fever. ASO is not useful for diagnosing a sore throat today, which needs a throat swab, and because many healthy children carry raised levels, a rising titre on two samples is more telling than one result.
What it measures: The level of antibodies against streptolysin O in serum, reported in IU/mL.
Parameters included (1)
- Anti-Streptolysin O (ASO) titre
Why is this test done?
- Supporting a diagnosis of acute rheumatic fever
- Investigating post-streptococcal glomerulonephritis, with dark or reduced urine and swelling
- Assessing joint pain that moves from joint to joint after a recent sore throat
- Showing evidence of a recent strep infection when a throat swab is negative
When should you get tested?
- Fever with painful, swollen joints that move from one joint to another, 2 to 4 weeks after a sore throat
- Cola-coloured or reduced urine with puffiness around the eyes after a throat or skin infection
- New chest pain, breathlessness or a heart murmur after a recent infection
- Jerky, uncontrolled movements in a child (Sydenham’s chorea)
- Skin nodules or a ring-shaped rash with fever and joint pain
How to prepare for the ASO Test
- 1No fasting is needed.
- 2Tell the staff when the sore throat or skin infection happened and whether antibiotics were taken, as early antibiotics can reduce the rise in ASO.
- 3If your doctor wants a rising titre, give the second sample 10 to 14 days after the first, at the same lab if possible.
ASO Test normal range
| Parameter | Typical reference range |
|---|---|
| Adults | Up to 200 IU/mL |
| Children (5 to 15 years) | Up to about 200–300 IU/mL; school-age children often run higher |
| Children under 5 | Usually lower, up to about 100 IU/mL |
Upper limits vary by age, region and method. A rise of two dilutions or more between two samples is more significant than a single value. Ranges are typical adult values and vary between labs, age and sex. Always use the range printed on your report and discuss results with your doctor.
Understanding your results
- A raised ASO shows a strep infection in the past few weeks to months. It supports, but does not by itself prove, rheumatic fever or kidney inflammation. Doctors use clinical criteria together with ECG, echocardiography or urine tests.
- A rising titre between two samples taken about 2 weeks apart is strong evidence of a recent infection.
- A normal ASO does not fully rule out a recent strep infection. Skin infections raise ASO less, and some people respond better to other strep antibodies such as anti-DNase B.
- A mildly raised ASO in a healthy child without symptoms is common and usually needs no treatment.
ASO Test – FAQs
What is the price of the ASO Test?
The Anti-Streptolysin O (ASO) Test costs ₹270 at Live Line Health Care, at all 45 centres and for home sample collection.
What does a high ASO titre mean?
It means you have had a streptococcal infection in the past few weeks to months. It does not mean you have rheumatic fever. Your doctor will look at symptoms such as joint swelling, heart findings and fever before deciding whether a post-strep condition is present and what treatment is needed.
Can ASO be used to diagnose a sore throat?
No. ASO rises a week or more after the infection, so it is too slow to diagnose a current sore throat. A throat swab culture or rapid strep test is used for that. ASO is useful later, when complications such as rheumatic fever are suspected.
How long does ASO stay high?
ASO usually peaks 3 to 5 weeks after the infection and then slowly declines, returning towards normal over about 6 to 12 months. A high value months later does not necessarily mean a new infection. Doctors read it alongside your symptoms and history.
Is ASO the same as a test for rheumatoid arthritis?
No. ASO looks for evidence of a recent strep infection, linked to rheumatic fever, which mostly affects children and young adults. Rheumatoid arthritis is a different long-term autoimmune condition, investigated with the RA factor and anti-CCP tests. The names sound similar, but the conditions are quite different.
Why is ASO tested in children with joint pain?
Acute rheumatic fever is most common between 5 and 15 years of age and can damage the heart valves. Joint pain that moves from joint to joint after a sore throat is a typical sign. ASO helps confirm a recent strep infection so that treatment and heart checks are not delayed.
Where can I get the ASO Test done?
At any of our 45 Live Line Health Care centres in 40 cities across Andhra Pradesh and Telangana, including Hyderabad, Visakhapatnam, Warangal, Kakinada and Nellore, or book home sample collection.
Medical disclaimer: This information is for general awareness only and is not a substitute for professional medical advice. Please consult a qualified doctor to interpret your results and before starting or changing any treatment.