Lab marker · High

High Anti-streptolysin O (ASO): what it means

A Anti-streptolysin O (ASO) result above the normal range is considered high. Here is what a raised Anti-streptolysin O (ASO) can point to, and when it is worth discussing with a doctor.

Reference range: typically <200 IU/mL in adults; a raised or rising level is evidence of a recent group A streptococcal infection — used mainly to support a diagnosis of rheumatic fever or post-strep kidney inflammation, not to diagnose an active sore throat

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What a high Anti-streptolysin O (ASO) can mean

  • A recent group A streptococcal infection — the level rises a week or two afterwards.
  • Acute rheumatic fever — supports the diagnosis alongside the clinical picture.
  • Post-streptococcal glomerulonephritis — a kidney inflammation following strep.
  • A rising level on paired samples — the most convincing evidence of recent infection.
  • A raised level from past exposure — common and not necessarily significant on its own.

When to discuss with a doctor

ASO is not a test for a current sore throat — a throat swab or rapid strep test is used for that. Instead it is requested when a doctor is investigating a possible complication of a recent strep infection, such as new joint pains, a heart murmur or signs of rheumatic fever, or blood and protein in the urine suggesting post-streptococcal kidney inflammation. A raised or, better, a rising ASO supports that a strep infection was the trigger, and is interpreted with the clinical picture and often a second antibody test. A high ASO on its own, without symptoms, usually just reflects a past infection and needs no action. Mediora.AI shows ASO alongside inflammatory markers so the post-strep pattern is visible; the interpretation and any diagnosis belong with your doctor.

Conditions this can relate to

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Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.