Patient education: Tests for strep throat (The Basics)

What is strep throat? — 

This is an infection caused by a certain type of bacteria (figure 1). It causes a sore throat.

Most sore throats are caused by a virus and are not strep throat. But if you do have strep throat, you need treatment with antibiotics.

How do doctors check for strep throat? — 

There are different types of testing for strep throat. For all of them, a doctor or nurse will rub the tip of a cotton swab along the back of your throat. This collects a sample to test.

Here are the 3 different types of tests for strep throat:

●Rapid antigen detection test – This is what most people think of when they hear "rapid strep test." It looks at the parts of the bacteria that cause strep throat. The results come back very quickly (usually within 15 minutes). This test is not as good at checking for strep throat as the others.

●Molecular test – This is a newer test that looks for genetic material from the bacteria. These are called "nucleic acid tests" or "PCR tests." Some offices have a rapid version of this test, and results can come back within 30 minutes. Other times, this test needs to be sent to a lab, and results come back in a day or 2. This test is very accurate.

●Throat culture – This might be done if the results from a rapid antigen test are not clear, the test is not available, or if your doctor thinks another type of bacteria could be causing your sore throat. A throat culture is sent to a lab for testing. In the lab, they rub the swab over a special culture plate that lets germs grow. If there are germs in the throat, they will show up within a few days. This test is very accurate.

How are strep throat tests done? — 

You do not need to do anything special to prepare for strep throat test.

The staff will use a flat stick called a "tongue depressor" to hold your tongue down and out of the way. Then, they will rub the swab over the back of your throat and tonsils. If they are doing more than 1 test (for example, a rapid antigen test and a throat culture), they might use 2 swabs.

When your throat is sore, rubbing the swab on your tonsils or throat might hurt a little. But the test only takes a few seconds.

What do my results mean? — 

If the doctor did an in-office strep test (either a rapid antigen test or a molecular test that comes back within 30 minutes), you will get results before leaving the office.

For tests sent to the lab, your doctor or nurse will tell you when to expect your results, and will contact you with the results. Or if you use an online "patient portal," you might get an alert there when your results are ready.

●If the test is "positive," this usually means you do have the strep bacteria in your throat. Your doctor or nurse will talk to you about what to do next. In most cases, they will prescribe an antibiotic to treat it.

●If the test is "negative," this usually means your sore throat is likely caused by something else. Your doctor might suggest other treatments to help with your sore throat.

A rapid antigen test is more likely than other tests to give a "false-negative" result. This is when the test comes back negative even though you actually do have strep throat. In some cases, your doctor might do a throat culture or molecular test to confirm the results.

More on this topic

Patient education: Strep throat in adults (The Basics)
Patient education: Strep throat in children (The Basics)
Patient education: Sore throat in adults (The Basics)
Patient education: Sore throat in children (The Basics)

Patient education: Sore throat in adults (Beyond the Basics)
Patient education: Sore throat in children (Beyond the Basics)