Strep Test

What is a strep test?

A strep test looks for infection caused by bacteria called group A streptococcus.

Why is this test done?

A strep test is done to find out if strep bacteria are causing a sore throat. If the test finds strep bacteria, your healthcare provider will probably prescribe antibiotics. Treatment with antibiotics may help you feel better sooner than if you do not have treatment. More importantly, it also lowers the chance of more serious problems that can be caused by strep, such as heart problems from rheumatic fever. Most other common causes of sore throat do not usually need treatment with antibiotics.

How do I prepare for this test?

The test is most accurate if you have not taken antibiotics before the test. Tell your healthcare provider if you took antibiotics during the 3 days before the test.

How is the test done?

The strep test may be done in 2 ways: a rapid strep test or a throat culture. For either test your healthcare provider gets a sample by rubbing a cotton swab against a tonsil in the back of the throat. The sample is sent to a lab.

• If the rapid strep test is done, the lab looks for a substance made by strep bacteria in the throat sample. If the test finds this substance, the result is positive and it means that strep bacteria were in the sample. The lab will have this result in 1 hour or less.
• If a throat culture is done, the lab checks for growth of bacteria from the sample. This test may be done to check the results of a rapid strep test. You can usually get these results in 24 to 48 hours.

Ask your healthcare provider when and how you will get the result of the test.

What does the test result mean?

Usually, a positive strep test means that you have strep, and a negative (normal) result means that you do not have strep.

Although these tests are very precise, they are not perfect. Cultures are more accurate and reliable than rapid tests. A culture may be done even though a rapid test is negative to make sure you do not have a strep infection. The strep culture test also provides more information than the rapid strep test. In addition to showing whether you have strep throat, it may show the specific kind (strain) of strep bacteria infecting your throat. It can help your healthcare provider know which antibiotic will be most effective in treating the infection. For this reason, your provider may not prescribe an antibiotic until the results of a culture test are back.

What if the test result is not normal?

If the test result is positive, ask your provider:

• what antibiotic he or she is prescribing
• if more tests are needed