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Lab Dept:


Test Name:


General Information

Lab Order Codes:



Antistreptolysin-O (ASO) Quantitative

CPT Codes:

86060 – Antistreptolysin O; titer

Test Includes:

Antistreptolysin O concentration reported in IU/mL. If anti-DNase B is also desired, see Streptococcal Antibodies


Test Indications:

Antistreptolysin O (ASO) titers are used to diagnose current versus past infections with group A streptococci. The test detects antibodies to Streptolysin O, one of the many streptococcal antigens. In addition, it may be used to help diagnose rheumatic fever.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test: ASO)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

1 – 3 days, testing performed Monday-Saturday

Special Instructions:



Specimen Type:



Red top (plain, no gel) tube

Draw Volume:

3 mL (Minimum: 1.5 mL) blood

Processed Volume:

1 mL (Minimum: 0.5 mL) serum


Routine venipuncture

Special Processing:

Lab Staff: Centrifuge specimen, remove serum aliquot into a plastic sample cup. Store at refrigerated temperatures.

Patient Preparation:

Fasting is preferred, but not required.

Sample Rejection:

Mislabeled or unlabeled; specimens other than serum; gross lipemia


Reference Range:


Range (IU/mL):

<5 years:

Less than or equal to 70 IU/mL

5 – 17 years:

Less than or equal to 640 IU/mL

≥18 years:

Less than or equal to 530 IU/mL

Interpretation: Elevated values are consistent with an antecedent infection by group A streptococci. Although the antistreptolysin O (ASO) test is quite reliable, performing the anti-DNase is justified because ASO response is not universal and elevated ASO titers are found in the sera of about 85% of individuals with rheumatic fever. ASO titers remain normal in about 15% of individuals with the disease. The same holds true for other streptococcal antibody tests. A significant portion of individuals with normal antibody titers for 1 test will have elevated antibody titers for another test. Thus, the percentage of false-negatives can be reduced by performing 2 or more antibody tests. Skin infections, in contrast to throat infections, are associated with a poor ASO response. Patients with acute glomerulonephritis following skin infection (post-impetigo) have an attenuated immune response to streptolysin O. For such patients, performance of an alternative streptococcal antibody test such as anti-DNase B is recommended.

Critical Values:



The use of the antistreptolysin O (ASO) for the diagnosis of an acute A streptococcal infection is rarely indicated, unless the patient has received antibiotics that would render the culture negative. There are a certain limitations to the use of the ASO test in these circumstances due to the delay and attenuation of the immune response following early antibiotic therapy.

False-high titers may be obtained wit sera that are contaminated by certain bacterial organisms during shipment or storage and n patients with liver disease where the presence of high lipoprotein concentrations in the serum may mimic antibody activity.




Mayo Medical Laboratories March 2014


3/24/2014: Moved from an internal test to Mayo.

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