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The Anti-Streptolysin O (ASO) Titre test measures the level of antibodies produced by the immune system against Streptolysin O...
Also known as: ASO Test · ASOT · Anti-Streptolysin O Test · Strep Antibody Test · Rheumatic Fever Test
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*Inclusive of home collection charges
The Anti-Streptolysin O (ASO) Titre test measures the level of antibodies produced by the immune system against Streptolysin O — a toxin secreted by Group A beta-haemolytic Streptococcus (GAS, or Strep A) bacteria. An elevated ASO titre confirms recent or ongoing streptococcal infection and is the primary test for diagnosing post-streptococcal complications — particularly Acute Rheumatic Fever (ARF) and post-streptococcal glomerulonephritis (PSGN). It is especially important in children presenting with joint pain, heart inflammation, or unexplained kidney disease following a throat or skin infection. No fasting required.
Key benefits of this package include:
What Does the Anti-Streptolysin O (ASO) Titre Test — Quantitative Measure?
| Level / Result | Possible Interpretation |
|---|---|
| Below reference range (Normal) | No evidence of recent Group A Streptococcus infection |
| Borderline elevation (200–400 IU/mL adults) | Possible recent strep infection — repeat in 2–4 weeks; rising titre is more significant than single reading |
| Significantly elevated (> 400 IU/mL) | Strong evidence of recent GAS infection — correlate with clinical symptoms of ARF or PSGN |
| Markedly elevated (> 800 IU/mL) | Recent or active streptococcal infection with significant immune response — high likelihood of post-strep complication |
| Declining ASO on serial testing | Recovering from GAS infection — immune response waning; monitor clinical response to treatment |
Important Note: A single elevated ASO titre indicates exposure to GAS but is not by itself diagnostic of ARF or PSGN — clinical criteria (Jones criteria for ARF) must also be met. Up to 20% of patients with culture-confirmed rheumatic fever may have a normal ASO — in which case Anti-DNase B (another streptococcal antibody) should be tested. All results should be reviewed by a physician or paediatrician.
ASO and Rheumatic Heart Disease Prevention: Acute Rheumatic Fever can cause permanent damage to the heart valves (rheumatic heart disease / RHD) — a major cause of acquired heart disease in children and young adults in India. Timely diagnosis of ARF using the ASO titre, followed by appropriate penicillin treatment and long-term penicillin prophylaxis, prevents recurrent streptococcal infections and progressive heart valve damage. Early detection through ASO testing is therefore a critical preventive health measure.
Trusted by millions of Customers across South India — these are the tests our doctors recommend most.
Screens for anaemia, infections, and immune health
