Anti-Streptolysin O Antibody (ASO) Blood Test

Anti-Streptolysin O Antibody (ASO) Blood Test

Quick Overview

This test is a sensitive test for recent streptococcal infection.

Test #265


Availability: In stock

Also Known As Streptolysin-O Antibody; Strep A; ASO; Streptococcus, Group A; ASLO Test; ASOT; Antistreptolysin O Titer

Fasting for 6 hours required.

Test Results 2-3 days. May take longer based on weather, holiday or lab delays.

The anti-streptolysin O antibody (ASO) blood test is primarily used to help determine whether a recent strep infection with group A streptococcus:

  • Is the cause of a person's or glomerulonephritis, a form of kidney disease
  • Caused rheumatic fever in a person with signs and symptoms

The test may be ordered by itself or along with an anti-DNase B, another test used to detect recent strep infections.

In most cases, strep infections are identified and treated with antibiotics and the infections resolve. In cases where they do not cause identifiable symptoms and/or go untreated, however, complications (sequelae), namely rheumatic fever and glomerulonephritis, can develop in some people, especially young children. The test, therefore, is ordered if a person presents with symptoms suggesting rheumatic fever or glomerulonephritis and has had a recent history of sore throat or a confirmed streptococcal infection. It is ordered when the symptoms emerge, usually in the weeks following a sore throat or skin infection when the bacteria are no longer present in the throat or on the skin.

Some symptoms of rheumatic fever may include:

  • Fever
  • Joint swelling and pain in more than one joint, especially in the ankles, knees, elbows, and wrists, sometimes moving from one joint to another
  • Small, painless nodules under the skin
  • Rapid, jerky movements (Sydenham's chorea)
  • Skin rash
  • Sometimes the heart can become inflamed (carditis); this may not produce any symptoms but also may lead to shortness of breath, heart palpitations, or chest pain

Some symptoms of glomerulonephritis may include:

  • Fatigue, decreased energy
  • Decreased urine output
  • Bloody urine
  • Rash
  • Joint pain
  • Swelling (edema)
  • High blood pressure

However, these symptoms can be seen in other conditions.

The test may be performed twice, with samples collected about two weeks apart, for acute and convalescent ASO titers. This is done to determine if the antibody level is rising, falling, or remaining the same.

Use of some antibiotics and corticosteroids may decrease ASO antibody levels.

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