Strep Test

What is a strep test?

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

Why is it done?

A strep test is done to find out if strep bacteria are causing a sore throat. If your health care provider finds that you have strep throat, he or she will prescribe antibiotics. Treatment with antibiotics may help your child feel better sooner and reduces the chance of developing more serious problems that can be caused by strep, such as heart problems. Strep is the only common cause of sore throat for which antibiotics are needed.

How should my child prepare for this test?

It is best not to take any antibiotics before a check for strep. Tell the health care provider if your child took antibiotics during the 3 days before the test.

How is the test done?

There are two types of strep tests: a throat culture and a rapid antibody test. For both tests your 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 antibody test is done, the lab checks for a chemical reaction between a protein (antigen) from strep bacteria and another protein (antibody) in the test kit. The lab will have the result in 1 hour or less. If the test is positive, it means that strep bacteria were in the sample from your throat.
• If a throat culture is done, the lab checks for growth of strep bacteria in the sample overnight. This test may be done to check the results of a rapid strep test. Results are usually available in 24 to 48 hours.

How will I get the test result?

Ask your health care provider when and how you will get the result of your child's test.

What does the test result mean?

Usually, a positive strep test result means that your child has strep, and a negative result means that your child does not have strep throat.

Although these tests are very precise, they are not perfect. Results of the rapid tests are wrong about 10% of the time. Cultures are wrong just 1% to 2% of the time if a good sample was used. To protect your child from getting heart or kidney complications caused by strep, antibiotics should be started no later than 7 to 10 days after your child gets the sore throat. This usually gives a health care provider plenty of time to check the result before prescribing antibiotics without any risk of complications.

If your test result is positive, ask your child's health care provider:

• which antibiotics should be prescribed
• if your child needs additional tests
• if your child needs to be tested again.