Antistreptolysin O titre

Antistreptolysin O titre (AS(L)O titre or AS(L)OT) - titre of (serum) antistreptolysin O antibodies; a blood test used to assist in the diagnosis of a streptococcal infection or indicate a past exposure to streptococci.

The ASOT helps direct the antimicrobial treatment and is used to assist in the diagnosis of scarlet fever, rheumatic fever and post infectious glomerulonephritis.

A positive test usually is &gt;200 units/mL, but normal ranges vary from laboratory to laboratory and by age.

The false negatives rate is 20-30%. If a false negative is suspected then an anti-DNase B titre should be sought. False positives can result from liver disease and tuberculosis.