Antistreptolysin O titre (ASOT) - serum

Last updated: Saturday, 16, June, 2007

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Item Process

5-10 mL blood in plain tube.


Inhibition of streptolysin-induced red cell lysis.

Reference Interval

Age dependent.

In adults, typically <166 Todd units, but consult pathologist.


To confirm exposure to Streptococcus pyogenes, in the investigation of rheumatic fever and acute glomerulonephritis.

Indicated occasionally in the investigation of severe cellulitis and rarely in recurrent tonsillitis.


A high titre, or a two fold rise in titre, indicates recent infection. Antibodies are not detected until at least 3 weeks post infection.

See also Antideoxyribonuclease B (AntiDNase B) antibodies - serum.


Martin DR. In: Stevens DL and Kaplan EL. Streptococcal Infections. Oxford University Press 2000.