Why are strep tests done?

Strep throat is a highly contagious bacterial infection of the throat. It’s caused by a type of bacteria called group A streptococcus (GAS).

If you see your doctor for a sore throat, they’ll likely use a rapid strep test to diagnose your condition. This involves taking a quick swab of your throat and examining it for signs of GAS. The results are ready in just a few minutes.

Doctors perform strep tests because the symptoms of strep throat can be similar to those of other conditions, including viral infections. Only bacterial infections, such as strep throat, will respond to antibiotics.

If your strep test comes back positive, you’ll likely be prescribed antibiotics. These will help to clear up the infection faster. Most people notice an improvement within a day or two.

Keep in mind that untreated strep throat can lead to several complications, including scarlet fever. If you think you or your child has strep throat, it’s important to diagnose and treat it early.

Today, you can sometimes purchase home strep tests from your local pharmacy. But do they work as well as the ones used by your doctor?

Home strep tests are pretty similar to the rapid strep test used by doctors. They come with a sterile cotton swab, which you’ll gently brush against the back of your throat for a second or two.

These tests typically come with two substances called reagents. You’ll mix these together and add the cotton swap. After letting everything sit for a few minutes, you’ll insert a small stick, which comes with the test.

Depending on the product you’re using, a line or series of lines will appear on the stick. These are your test results.

Rapid strep tests aren’t 100 percent accurate. According to a 2016 review, they correctly identify strep throat in 86 percent of people who have it. Based on these results, the test would return a negative result for 14% of those who have strep throat. This is known as a false negative result.

It’s also important to use strep tests correctly for the most accurate results. Doctors and nurses go through training to learn how to effectively collect throat swabs. But for someone without any medical training, it can be hard to do initially.

Still, a 2017 study found that, under supervision of clinic staff, 71 out of 76 parents were able to successfully obtain a throat swab sample from their child after watching a short instructional video.

If your child gets sore throats often, considering asking a doctor to show you how to properly collect a throat swab on your own.

But home tests still carry the same risk of producing a false negative. Doctors can combat this by doing a throat swab culture. This involves taking collecting another throat swab and sending it off to a lab.

If you have strep throat, the lab will be able to grow GAS bacteria from your sample. This test isn’t available for home use, and the results take a few days to come in.

To ensure that you get the most accurate results, check the stick that comes with your strep test for something called a control line. This should be visible on the stick, regardless of your test results. This line lets you know the test is working properly. If you don’t see a control line on your stick, discard it and try a new test.

Negative result

A negative result could mean that you or your child doesn’t have strep throat. But it could also be a false negative, meaning your or your child actually do have strep throat.

If your results are negative, it’s still a good idea to follow up with a doctor for a throat culture or exam. Remember, strep throat can lead to other health problems if left untreated, especially in children.

Positive result

If your results are positive, you may have saved yourself a trip to the doctor. This means that they test detected GAS bacteria in your sample. But you’ll still need to contact your doctor in order to get a prescription for antibiotics. Depending on your doctor, you may still have to go into their office to get this prescription.

Regardless of the results of a home strep test, it’s still best to see a doctor if you or your child have:

  • a sore throat that lasts longer than two days
  • a fever that’s higher than 101°F or lasts longer than two days
  • a sore throat with tender or swollen lymph nodes
  • trouble breathing or swallowing
  • a sore throat with an accompanying rash
  • a strep throat diagnosis with no improvement after two days of antibiotic treatment

Home strep tests can be an affordable, convenient way to test for strep throat without a visit to the doctor’s office. Using a simple sample collection and testing process, results are available in minutes.

However, rapid strep tests can sometimes give a false negative result, so it’s still a good idea to follow up with a doctor if your results are negative.