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Antistreptococcal Antibody Titers

What Is An Antistreptococcal Antibody Titer?

An antistreptococcal (strep) antibody titer is a blood test. The test is done to see if a person has been infected with strep. Strep (streptococcus) is a type of bacteria.

A titer measures how much of an antibody is in the blood. An antibody is a protein made by the immune system. It helps to fight infections. This titer measures strep antibodies.

Reason for the Test

The test is given to look for problems caused by a strep infection, such as:

  • Inflammation of the tonsils
  • Skin infections
  • Rheumatic fever (RF)
  • Post-strep glomerulonephritis—a kidney problem
  • Scarlet fever

Type of Sample Taken

Blood is taken from a vein in the arm.

Prior to Collecting the Sample

Nothing needs to be done before the test.

During the Sample Collection

You will be asked to sit. An area on your arm will be cleaned with a wipe. A large band will be tied around your arm. The needle will be put in a vein. A tube will collect the blood from the needle. The band on your arm will be taken off. After the blood is collected, the needle will be removed. Gauze will be held on the site to help stop bleeding. You may also be given a bandage. This test takes about 5 to 10 minutes.

After Collecting the Sample

After the blood sample is taken, you may need to stay seated for 10 to 15 minutes. If you are lightheaded, you may need to stay seated longer. When you feel better, you can leave.

A bit of blood may ooze from the vein beneath the skin. It will cause a bruise. A bruise will usually fade in a day or two.

Call your doctor right away if you have redness, swelling, lasting bleeding, or pain.


Several tests are usually done. This is to watch for changes in titer levels over a time period.

Tests results may be ready in a few days. Test results may mean:

  • A negative test or very low titers—there was likely no recent strep infection.
  • A high number of titers shows a current or recent infection.

Talk to your doctor about your test results. A test can point to an illness that you do not have. It can also miss an illness that you may have. The doctor will check your symptoms and all test results before making a diagnosis.


Antistreptolysin O (ASO). Lab Tests Online website. Available at: https://labtestsonline.org/tests/antistreptolysin-o-aso. Accessed August 19, 2021.

Group A streptococcus. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/group-a-streptococcus. Accessed August 19, 2021.

Streptococcal antibodies. Children's Minnesota website. Available at: https://www.childrensmn.org/references/lab/serology/streptococcal-antibodies.pdf. Accessed August 19, 2021.

Last reviewed July 2021 by David L. Horn, MD, FACP  Last Updated: 8/19/2021