Book ASO Test: Purpose, Normal Range and Price

The ASO test, or Anti Streptolysin O test, is a blood test that measures antibodies produced against streptolysin O, a toxin released by Group A Streptococcus bacteria. These antibodies rise 1 to 3 weeks after infection and can remain elevated for months, confirming that a recent or past streptococcal infection has occurred rather than detecting active infection directly. In India, Group A Streptococcal infections remain highly prevalent in children and adolescents, and untreated infections can trigger serious immune-mediated complications including acute rheumatic fever, rheumatic heart disease, and post-streptococcal glomerulonephritis. Rheumatic heart disease remains one of the leading causes of acquired heart disease in Indian children and young adults, making the ASO test a critically important diagnostic marker following any sore throat, joint pain, or unexplained kidney disease. The test involves a simple blood draw completed in under five minutes.

Doctors prescribe an ASO test in the following situations: Diagnosing acute rheumatic fever in patients with joint pain, fever, and carditis following a recent sore throat, where an elevated ASO titre confirms the preceding streptococcal infection required to meet the Jones criteria for diagnosis. Evaluating a new heart murmur or carditis in children and young adults where rheumatic heart disease must be confirmed or excluded alongside clinical and echocardiographic findings. Investigating post-streptococcal glomerulonephritis in patients with blood in the urine, swelling, and elevated blood pressure following a recent throat or skin infection, where elevated ASO confirms the streptococcal trigger. Evaluating joint pain and arthritis in children where reactive post-streptococcal arthritis must be distinguished from juvenile idiopathic arthritis and other inflammatory conditions requiring different management. Investigating Sydenham's chorea in children with involuntary movements following a recent streptococcal infection, where elevated ASO confirms the underlying post-streptococcal autoimmune mechanism. Monitoring patients with established rheumatic heart disease on long-term penicillin prophylaxis where periodic ASO titres assess the effectiveness of secondary prevention against recurrent streptococcal infections. Evaluating unexplained fatigue, fever, and malaise in children following a recent throat infection where subclinical rheumatic fever or post-streptococcal reactive syndromes must be considered.

The ASO test measures the concentration of Anti Streptolysin O antibodies in the blood, reported in International Units per millilitre (IU/mL). Normal ASO Range in India The standard reference ranges used across most Indian diagnostic laboratories are as follows. For adults, a normal ASO titre is below 200 IU/mL. For children below 5 years, the normal upper limit is below 100 IU/mL. For school-age children between 5 and 15 years, the upper limit is below 150 to 200 IU/mL. In India, background ASO titres are naturally higher than Western reference ranges due to endemic streptococcal exposure, and mildly elevated single values must be interpreted cautiously alongside clinical history. Interpreting ASO Results An ASO titre above the age-appropriate upper limit indicates recent or past Group A Streptococcal infection. A rising titre on repeat testing two to four weeks apart is more diagnostically significant than a single elevated value and provides stronger evidence of a recent streptococcal trigger. A normal ASO titre does not completely exclude streptococcal infection as approximately 20% of rheumatic fever patients may have a normal ASO. Anti-DNase B is recommended alongside ASO for the most complete assessment, particularly in skin infection-triggered complications.

No fasting is required for the ASO test. You can eat and drink normally before sample collection. Our team confirms preparation requirements at the time of booking. Inform the phlebotomist about all antibiotics and anti-inflammatory medications you are currently taking, as early antibiotic treatment can blunt the ASO antibody response and produce a lower than expected titre. Inform your doctor about the timing of any recent throat or skin infection, as the ASO test is most informative when performed 2 to 4 weeks after the suspected streptococcal infection onset. Stay normally hydrated before sample collection.

If you are booking through the SecondMedic platform the ASO test price starts at approximately Rs. 668. The exact price will be confirmed at the time of booking through SecondMedic. If your doctor has prescribed multiple tests alongside ASO, SecondMedic health packages include ASO as part of a broader rheumatic fever, autoimmune, or paediatric infection panel at a significantly lower combined price.

SecondMedic provides home sample collection for ASO test across all major areas in India. You do not need to visit a lab or collection centre. A certified and trained phlebotomist comes to your home or workplace at your chosen time, collects the sample using sterile single-use equipment, and ensures it is transported to the NABL-accredited lab within the required time window for accurate processing. Please note that SecondMedic provides free home sample collection on all tests priced above Rs. 300. Our team will check your pincode and confirm if your address falls under our free sample collection eligibility criteria, which depends upon the lab location and phlebotomist availability. Home collection is available between 7 AM and 10 PM, seven days a week, including Sundays and public holidays. Enter your pincode on the booking page or call our helpline to confirm availability at your address.