An antibody, anti-streptolysin O, can be detected in an antistreptolysin O titre.

There will be an elevated Anti-streptolysin O titre and low complement levels (C3 and C4) in the blood.

An anti-streptolysin O titre (or ASOT) is typically done to test for exposure to streptococci.

Anti-streptolysin O (ASO or ASLO) is the antibody made against streptolysin O, an immunogenic, oxygen-labile hemolytic toxin produced by most strains of group A and many strains of groups C and G streptococci.