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Anti-streptolysin O, Streptococcal Anti-hemolysin


Anti-streptolysin O (ASO) is the main antibody produced by the body in response to a group A beta-hemolytic streptococcal infection (strep A). This bacteria is responsible for many throat infections and usually responds well to antibiotic treatment. If a strep A infection is not diagnosed or is poorly treated, the toxin produced by the bacteria (streptolysin O) can lead to complications such as acute rheumatism or glomerulonephritis (kidney inflammation). ASO antibodies develop one week to one month after a strep A infection and peak about 4 to 6 weeks after onset of the disease and then decrease, but may remain detectable for several months after recovery.

A negative or very low result, especially if repeated 10 to 14 days later, indicates that the person probably did not have a recent strep A infection, but there are rare exceptions. If the concentration is high or increasing, a recent strep A infection is very likely. An ASO blood test cannot be used to predict whether complications will occur, or to predict the type and severity of the disease. If symptoms of rheumatic fever or glomerulonephritis are present, a high ASO titre will help confirm the diagnosis.

Term of the Week

Hot zone

A hot zone is a section of a facility (sometimes an entire facility or even a city district) where there is a high risk of contamination by patients with an infectious disease. All individuals entering a hot zone must respect appropriate protective measures. By analogy, “cold zone” and “warm zone” are used to refer to areas where there is no infected individual or only individuals suspected of having an infection.