LabCorp

Antistreptolysin O Ab

Optimal Result: 0 - 200 IU/ml.

Antistreptolysin O (ASO) is an antibody targeted against streptolysin O, a toxic enzyme produced by group A Streptococcus bacteria. ASO and anti-DNase B are the most common of several antibodies that are produced by the body’s immune system in response to a strep infection with group A Streptococcus. This test measures the amount of ASO in the blood.

Group A Streptococcus (Streptococcus pyogenes) is the bacterium responsible for causing strep throat and a variety of other infections, including skin infections (pyoderma, impetigo, cellulitis). In most cases, strep infections are identified and treated with antibiotics, and the infections resolve.

-------------------

The ASO test is ordered when a person has symptoms that a health practitioner suspects may be due to an illness caused by a previous strep 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 amount of urine
- 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.

-------------------

Streptolysin is a hemolysin produced by group A streptococci. In an infected individual streptolysin O acts as a protein antigen, and the patient mounts an antibody response. A rise in antibody level begins about one week after infection and peaks two to three weeks later. In the absence of complications or reinfection, the ASO titer will usually fall to preinfection levels within 6 to 12 months. Both clinical and laboratory findings should be correlated in reaching a diagnosis.

The ASO test does not predict whether complications will occur following a strep infection, nor does it predict the type or severity of the disease. If symptoms of rheumatic fever or glomerulonephritis are present, an elevated ASO level may be used to help confirm the diagnosis.

ASO antibodies are produced about a week to a month after an initial strep infection. The amount of ASO antibody (titer) peaks at about 3 to 5 weeks after the illness and then tapers off but may remain detectable for several months after the strep infection has resolved. Over 80% of patients with acute rheumatic fever and 95% of patients with acute glomerulonephritis due to streptococci have elevated ASO. A negative ASO or ASO that is present at very low titers means the person tested most likely has not had a recent strep infection. This is especially true if a sample taken 10 to 14 days later is also negative (low titer of antibody) and if an anti-DNase B test is also negative (low titer of antibody). A small percentage of people with a complication related to a strep infection will not have an elevated ASO. This is especially true with glomerulonephritis that may develop after a skin strep infection.

Since the incidence of post-streptococcal complications has dropped in the U.S., so has the use of the ASO test.

What does it mean if your Antistreptolysin O Ab result is too high?

An elevated titer of antibody (positive ASO) or an ASO titer that is rising means that it is likely that the person tested has had a recent strep infection. ASO titers that are initially high and then decline suggest that an infection has occurred and may be resolving.

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 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.

Understand blood, stool, and urine medical results from your labs.

10 000+ happy clients
100% satisfaction
★★★★★ customer support

Get 10% off of your first yearly or monthly plan.

Use promocode

Essential Plan


  • Monthly subscription
  • Instant interpretation
  • Use the free self-upload form
  • Additional charge for upload service
  • 2000+ biomarkers explained
  • Recommendations
  • Cancel anytime

Advanced Plan


  • Yearly subscription
  • Instant interpretation
  • We upload five reports for you
  • Use the free self-upload form
  • 2000+ biomarkers explained
  • Nutrition Recommendations
  • Online support
  • Cancel anytime

Own It For Life premium plan


  • No subscription
  • Unlimited access
  • Unlimited storage
  • Instant interpretations
  • We upload ten reports for you
  • Use the free self-upload form
  • 2000+ biomarkers explained
  • Nutrition Recommendations
  • Dedicated support

Healthmatters.io software for professional use.

Welcome to Healthmatters Pro.

Save time on interpreting lab results with the largest database of biomarkers online. In-depth research on any test at your fingertips, all stored and tracked in one place.

Learn More


We implement proven measures to keep your data safe.

At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put industry-leading security standards in place to help protect against the loss, misuse, or alteration of the information under our control. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details.

General Data Protection Regulation (GDPR). HIPAA compliance for healthcare professionals
×

Understand Your Lab Result Now

  • Instant interpretation
  • 2000+ biomarkers explained
  • Science-based recommendations
  • Online support
  • Secure and private portal

Get 10% off with promocode:

;