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Antistreptolysin 0; titer

CPT4 code

Antistreptolysin O Titer

Name of the Procedure:

Common Names: Antistreptolysin O Test, ASO Titer
Technical/M edical Term: Antistreptolysin O Titer


The Antistreptolysin O (ASO) titer is a blood test that measures the level of antistreptolysin O antibodies in the bloodstream. High levels of these antibodies indicate a recent streptococcal infection.


The ASO titer test helps diagnose a recent streptococcal infection, which can be associated with conditions such as rheumatic fever or glomerulonephritis. The goal is to confirm the presence of streptococcal antibodies to guide appropriate treatment.


  • Recent history of symptoms suggestive of streptococcal infection (sore throat, skin infections).
  • Symptoms indicative of complications from a streptococcal infection, such as joint pain or swelling (suggestive of rheumatic fever) or blood in the urine (indicative of glomerulonephritis).


  • There are no specific preparations required for an ASO titer test.
  • Patients should inform their healthcare provider about any medications they are taking as certain drugs might affect the results.

Procedure Description

  1. A healthcare professional will clean the skin area and insert a needle into a vein, usually in the arm.
  2. Blood is drawn into a vial or syringe.
  3. The blood sample is sent to a laboratory for analysis to measure ASO antibody levels.
  4. The entire process usually takes a few minutes.


The blood draw typically takes less than 10 minutes. Lab results usually come back within a few days.


This test can be performed in various settings, including hospitals, outpatient clinics, and specialized laboratories.


Generally, a phlebotomist or nurse performs the blood draw, while a laboratory technician analyzes the blood sample.

Risks and Complications

  • Minor risks include discomfort, bruising, or bleeding at the puncture site.
  • Rarely, some patients may feel light-headed or faint.


  • Helps in the accurate diagnosis of a recent streptococcal infection.
  • Guides appropriate treatment to prevent complications such as rheumatic fever or kidney damage.


  • No special post-procedure care is required.
  • Patients can resume normal activities immediately after the blood draw.


  • Other diagnostic tests for streptococcal infections include throat cultures and rapid antigen detection tests.
  • Pros and cons: Throat cultures and rapid tests are more immediate for diagnosing active infections, while the ASO titer is useful for identifying past infections and related complications.

Patient Experience

  • Patients may feel a quick pinch when the needle is inserted.
  • Mild bruising or soreness at the puncture site is possible but typically resolves quickly.
  • Pain management is generally unnecessary, but comforting measures include applying a warm compress to the puncture site if discomfort occurs.