Antistreptolysin O titre

Keywords: ASOT

Specimen:

5-10 mL blood in plain tube.

Method:

Inhibition of streptolysin-induced red cell lysis.

Reference Interval:

Age dependent.

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

Application:

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.

Interpretation:

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 Anti-deoxyribonuclease B Ab.

Reference:

Martin DR. In: Stevens DL, Kaplan EL. Streptococcal Infections. New York: Oxford University Press, 2000.