Strep throat is diagnosed with a quick swab of the back of your throat, and in most cases you can get results within minutes. There are three main types of tests used, and which one you get depends on your age, your symptoms, and what your healthcare provider’s office has available.
The Rapid Strep Test
The most common first step is a rapid antigen detection test, often just called a “rapid strep test.” It works by detecting specific proteins on the surface of Group A Streptococcus bacteria. A provider swabs the back of your throat, dips the swab into a chemical solution, and the test produces a result in about 5 to 10 minutes.
The rapid test is good at confirming strep when it’s present, but it misses some cases. A positive result is reliable and typically means you’ll be prescribed antibiotics right away. A negative result, however, doesn’t always rule strep out, which is why a second test is sometimes needed.
Throat Culture: The Backup Test
A throat culture is the gold standard for strep diagnosis. It’s collected the same way: a provider tilts your head back, presses your tongue down with a tongue depressor, and rubs a cotton swab along the back of your throat. That sample goes to a lab where it’s mixed with chemicals that encourage bacterial growth.
The tradeoff is time. Results from a throat culture typically take two to seven days, so it’s not useful when you need an answer on the spot. That’s why most offices start with the rapid test and only send a culture if the rapid result is negative and strep is still suspected.
CDC guidelines make an important distinction here based on age. For children older than 3, a negative rapid test should be followed up with a throat culture, because children face a higher risk of complications like rheumatic fever. For adults, a backup culture after a negative rapid test isn’t routinely recommended, since rheumatic fever is very rare in older age groups.
Molecular (PCR) Testing
Some clinics now use molecular tests that detect the DNA of strep bacteria rather than surface proteins. These are significantly more accurate than standard rapid tests. In a study comparing molecular testing to culture in a pediatric outpatient setting, the molecular test showed 98% sensitivity and 100% specificity, meaning it caught nearly every true case and produced virtually no false positives.
Because of this accuracy, some experts argue that molecular tests can be used as a standalone diagnostic tool without a backup culture. However, the FDA still recommends confirming negative molecular results with a culture, so practice varies by clinic. If your provider uses a molecular test, you may not need a follow-up culture at all, but it’s worth asking.
What Happens During the Swab
Regardless of which test is ordered, the swab itself is the same brief procedure. You’ll be asked to open your mouth wide and say “ahhh.” The provider needs to swab very specific areas: the surface of one or both tonsils, the tonsillar pillars (the arches of tissue on either side of the tonsils), or the back wall of the throat. Swabbing the wrong area, like the tongue, gums, or inside of the cheeks, can lead to a false negative result.
The swab takes only a few seconds. It can trigger a gag reflex and feels uncomfortable, but it isn’t painful. For young children, a parent may need to help hold the child still so the provider can get a clean sample from the right spot.
How Providers Decide Whether to Test
Not every sore throat warrants a strep test. Providers use a clinical scoring system called the Centor tool to estimate the likelihood of a bacterial infection before ordering any test. The score is based on five factors: your age, whether you have swollen lymph nodes in the neck, the presence or absence of a cough, whether you have a fever, and whether there’s white or yellow coating on your tonsils. Each factor adds or subtracts a point, producing a score from negative 1 to 5.
A low score suggests a viral infection is more likely, and testing may not be necessary. A higher score raises the probability of strep and makes testing worthwhile. This is why a provider might examine you and decide not to test at all, even if your throat is sore. Cough, runny nose, and hoarseness all point toward a virus rather than strep, and testing in those cases often produces misleading results.
Can You Test for Strep at Home?
At-home strep test kits do exist, but no over-the-counter strep test is currently FDA-approved for use by non-medical professionals. The tests you might find online are generally cleared only for use by licensed providers, or they’re non-FDA-approved products with unreliable accuracy.
When performed correctly, at-home rapid tests detect strep about 86% of the time and correctly identify negative cases about 95% of the time. That sounds reasonable, but the “performed correctly” part is key. Getting a good swab from your own throat is difficult, and an inadequate sample drops accuracy further. If you suspect strep, an in-office test remains the most reliable option, especially for children where missed cases carry higher stakes.
What to Expect After Testing
If your rapid test comes back positive, treatment with antibiotics usually starts the same day. You can expect to feel noticeably better within 24 to 48 hours of starting medication, and you’re generally considered no longer contagious after about 12 to 24 hours on antibiotics.
If the rapid test is negative but your provider sends a backup culture, you’ll need to wait for those results before a final answer. The office should contact you if the culture comes back positive, at which point antibiotics would be prescribed. In the meantime, over-the-counter pain relievers and throat lozenges can help manage symptoms while you wait.