Antistreptolysin O (ASO) titre

The ASO test is used to assess the antibody titre produced by the body in response to streptolysin, a protein with haemolytic action released by group A Streptococcus. The level of anti-streptolysin starts to rise as early as a week after Streptococcus infection and reaches a peak within about a month and returns to normal values after a varying period of time (which may last a year).

Streptococcal infections  usually resolve easily with antibiotic therapy. However, in some cases, the infection may lead to more or less severe complications such as glomerulonephritis or rheumatic fever. Evaluation of ASO is important for diagnosing a recent Streptococcus type A infection, especially in the case of acute infections.