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Test ID ASO Antistrep-O Titer, Serum

Useful For

Demonstration of acute or recent streptococcal infection

Reporting Name

Antistrep-O Titer, S

Specimen Type


Ordering Guidance

Patients with acute glomerulonephritis following skin infection (post-impetigo) have an attenuated immune response to streptolysin O. For these patients, performance of an alternative streptococcal antibody test such as ADNAS / Anti-DNase B Titer, Serum is recommended.

Specimen Required

Patient Preparation: Fasting preferred but not required


Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  7 days

Clinical Information

A number of bacterial antigens have been identified in cultures of group A streptococci. These extracellular products are primarily enzymatic proteins and include streptolysin O, streptokinase, hyaluronidase, deoxyribonucleases (DNases A, B, C, and D), and nicotinamide adenine nucleotidase.


Infections by the group A streptococci are unique because they can be followed by the serious nonpurulent complications of rheumatic fever and glomerulonephritis. Recent information suggests that rheumatic fever is associated with infection by certain rheumatogenic serotypes (M1, M3, M5, M6, M18, and M19), while glomerulonephritis follows infection by nephritogenic serotypes (M2, M12, M49, M57, M59, and M60).


Glomerulonephritis and rheumatic fever occur following the infection, after a period of latency following the infection, during which the patient is asymptomatic. The latency period for glomerulonephritis is approximately 10 days, and for rheumatic fever the latency period is 20 days.

Reference Values

<5 years: ≤70 IU/mL

5-17 years: ≤640 IU/mL                

≥18 years: ≤530 IU/mL


Elevated values are consistent with an antecedent infection by group A streptococci.

Clinical Reference

Ayoub EM, Harden E: Immune response to streptococcal antigens: diagnostic methods. In Manual of Clinical and Laboratory Immunology. Fifth edition. Edited by NR Rose, EC de Marco, JD Folds, et al. Washington, DC, ASM Press, 1997

Day(s) Performed

Monday through Friday

Report Available

Same day/1 to 3 days

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
ASO Antistrep-O Titer, S 5370-2


Result ID Test Result Name Result LOINC Value
ASO Antistrep-O Titer, S 5370-2

Method Name