Laboratory Test Information Guide

Details for Anti Streptolysin O Screen

Test Name: Anti Streptolysin O Screen
Alternate Name(s): ASO Screen and Titre
Laboratory: Virology Laboratory
Specimen Type: 5 mL Gold or 6 mL Red top Vacutainer tube
Collection Information: Minimum volume required is 1 mL.
Test Schedule: Testing is performed daily, Monday-Friday
Turnaround time from when specimen
is received in testing laboratory:
1 day
2 hours
Reference Range: A detectable level of 200 IU/mL ASO antibodies is usually regarded as the normal upper limit since less than 15-20% of healthy individuals demonstrate titres greater than 200 IU/mL when their sera are assayed. In most newborns the titre is initially greater than that of the mother due to maternally acquired IgG but the levels fall sharply during the first weeks of life.

Normal ASO levels for preschool children are generally less than 100 IU/mL but the levels rise with age, peaking in school age and decreasing in adulthood.

Increases in ASO titre generally occur one to four weeks after onset of infection with B-hemolytic streptococci Group A. As the infection subsides, the titre declines and returns to normal levels within six months. If the titre does not decrease, a recurrent of chronic infection may exist.

Elevated ASO titres may be associated with ankylosing spondylitis glomerulonephritis, scarlet fever, and tonsilitis. Increased ASO levels are generally not found in sera of patients with rheumatoid arthritis except during acute episodes.

Extremely low levels of ASO have been observed in the blood samples of patients with nephrotic syndrome and antibody deficiency syndromes.
Effective Date: 2006-11-16
Revised Date: 2020-02-12
Critical Value:  
Interpretive Comments: Screen detects antibodies to the enzyme streptolysin O. If screen test is positive, a semi-quantitative method will be done (antistreptolysin O titre/ASOT).
Special Processing:  
Method of Analysis: Slide agglutination
Critical Information Required:  
Storage & Shipment: Specimen must be received within 24 hours of collection. If the transport time exceeds 24 hours, the specimen will only be tested if appropriate.
System Codes: 
Referred To:  

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