Antistreptolysin-O (ASO)

Test Code

Quest Code

Alias/See Also

CPT Codes

Preferred Specimen
1 mL serum

Minimum Volume
0.5 mL

Transport Container
Preferred: Gold top; Acceptable: Plain red top

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 72 hours
Refrigerated: 5 days
Frozen: 30 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis


Setup Schedule
Cut-off 8: 00am, exp rel 5: 30pm M-f

Report Available
3 days

False-positive ASO titers can be due to increased levels of serum beta-lipoprotein produced in liver disease and by "contamination" of serum by Bacillus cereus and Pseudomonas species. ASO is not sensitive for the diagnosis of streptococcal pyoderma.

Reference Range
<5 Years <100 IU/mL 
5-20 Years <250 IU/mL
≥21 Years <200 IU/mL 

Clinical Significance
This test is a sensitive test for recent streptococcal infection. A rise in ASO begins about one week after infection and peaks two to four weeks later. ASO levels do not rise with cutaneous infections. In the absence of complications or reinfection, the ASO level will fall to preinfection levels within 6 to 12 months. Over 80% of patients with acute rheumatic fever and 95% of patients with acute glomerulonephritis due to streptococci have elevated levels of ASO.

Performing Laboratory
Quest Diagnostics - South Region

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.