Asl

Antibodies against the bacterial exotoxin streptolysin O. Antistreptolysin-AK forms the immune system in an infection with beta-hemolytic streptococci. Antibodies are determined from serum by ELISA and expressed as antistreptolysin titres. The ASL titer has a relatively low sensitivity and specificity. Therefore, the determination of additional laboratory parameters such as anti-DNase B and anti-hyaluronidase is recommended for diagnostic confirmation.

The reference range is for adults < 200 IU/ml and for children < 400 IU/ml

Elevated antistreptolysin O levels are found 7-21 days after streptococcal infection. Maximum values are reached after about 3-5 weeks. After about ½ year the values return to normal. Persistent, high values indicate a chronic (possibly requiring treatment) focus of inflammation.

1. Blyth CC et al (2006) Anti-streptococcal antibodies in the diagnosis of acute and post-streptococcal disease: streptokinase versus streptolysin O and deoxyribonuclease B. Pathology 38:152-156
2. Sen ES et al (2014) How to use antistreptolysin O titre. Arch Dis Child Educ Pract Ed 99:231-238