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Beta Hemolytic Streptococcus Culture (Throat)

Does this test have other names?

Strep test, throat culture

What is this test?

This test looks for the bacteria that cause strep throat. This condition causes a severe sore throat and makes it painful to swallow. It's important to detect and treat strep throat as soon as possible because it can progress to more serious illnesses, such as rheumatic fever.

The bacteria most likely to cause strep throat and bacterial sore throats in general are called Group A beta-hemolytic Streptococcus pyogenes (GABHS).

This test is a highly reliable way to diagnose strep throat because it has a sensitivity of 90 to 95 percent. But it's not used as commonly as the rapid antigen test because results for the throat culture are usually not available until 24 to 48 hours later.

Why do I need this test?

You may need this test if you have symptoms of strep throat, including:

  • Sore throat

  • Fever

  • Chills

  • Headache

  • Mild neck stiffness

  • Appetite loss

  • Swollen or enlarged lymph nodes

  • Rash

You may also have this test if your tonsils are painfully enlarged and your breath smells very bad.

Strep throat is treated with antibiotics. Starting antibiotics immediately eases symptoms and can reduce the time you are contagious from one week to one day. Treatment also prevents rheumatic fever if taken within 10 days after symptoms begin.

What other tests might I have along with this test?

Your doctor may also order these tests:

  • Rapid antigen test

  • Clinical prognostic score for GABHS, a score that helps prevent overuse of antibiotics for sore throats 

What do my test results mean?

Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.

Normal results are negative, meaning you don't have strep throat. If your test result is positive, you almost certainly have strep throat caused by GABHS.  If your sore throat lasts longer than a week, you probably have a different illness.

How is this test done?

The test requires a sample from your throat. Your doctor will take the sample by swabbing both of your tonsils.

Does this test pose any risks?

The swabbing may cause a slight discomfort.

What might affect my test results?

Taking antibiotics can affect your results.

How do I get ready for this test?

You don't need to prepare for this test. But be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.