A strep throat test detects whether Group A Streptococcus bacteria are causing your sore throat. The most common version is a rapid test done in a doctor’s office or urgent care that gives results in about 10 minutes. If that comes back negative, a throat culture may be sent to a lab, which takes one to two days. The reason testing matters: strep throat requires antibiotics, and most sore throats (caused by viruses) don’t.
What Happens During the Test
The test itself is quick and straightforward. A healthcare provider uses a long cotton swab to collect a sample from the back of your throat and tonsils. You’ll need to open your mouth wide, and the provider will press down on your tongue with a flat stick to get clear access. The swab takes just a few seconds, though it can trigger a brief gag reflex. That’s the uncomfortable part, and it’s over fast.
The swab is then either tested on-site with a rapid kit or sent to a lab for a culture. In many cases, both happen: the rapid test is run first for a quick answer, and if it’s negative, the same swab (or a second one) goes out for culture to make sure nothing was missed.
Types of Strep Tests
There are three main ways to test for strep, and they differ in speed, accuracy, and where they’re performed.
Rapid Antigen Test
This is the standard point-of-care test you’ll encounter at most clinics. It works by exposing your throat swab sample to antibodies that react specifically to a carbohydrate on the surface of strep bacteria. If strep is present, the antibodies bind to it and produce a visible line on a test strip, similar to how a pregnancy test works. Results appear in 5 to 10 minutes. The trade-off for that speed is accuracy: rapid tests catch about 70% to 90% of true strep cases, meaning some infections slip through. When they do detect strep, though, they’re right about 95% to 98% of the time.
Throat Culture
A throat culture remains the gold standard for diagnosing strep. The lab places your swab sample on a growth plate and waits to see if strep bacteria multiply over 24 to 48 hours. It’s more accurate than a rapid test, but the wait means you won’t get same-day results. Cultures are most commonly used as a backup when a rapid test is negative but strep is still suspected.
Molecular (PCR) Test
Newer molecular tests use DNA amplification technology to detect strep genetic material directly. These combine the best of both worlds: sensitivity around 98% (comparable to culture) with results in 15 to 24 minutes. They’re becoming more available in clinics and urgent care centers, though they aren’t yet as widespread as traditional rapid tests.
Who Gets Tested and Why
Not every sore throat warrants a strep test. Providers use a scoring system called the McIsaac score to decide whether testing makes sense. It evaluates five factors: your age, whether you have a fever, swollen or coated tonsils, tender lymph nodes in the front of your neck, and the absence of a cough. Each factor adds a point. A score of 3 or higher generally means you should be tested. A lower score suggests a viral cause, and testing usually isn’t recommended because the chance of strep is low enough that a positive result could just reflect harmless bacterial carriage rather than active infection.
This matters because about 20% to 30% of childhood sore throats are caused by strep, while the vast majority in adults are viral. Testing helps sort out which is which so antibiotics are prescribed only when they’ll actually help.
Children vs. Adults
Testing guidelines differ by age in one important way. When a child’s rapid test comes back negative, providers typically follow up with a throat culture to confirm the result. That’s because strep is more common in children, the rapid test’s sensitivity is imperfect, and the consequences of a missed diagnosis (particularly rheumatic fever) are more serious in younger patients. For adults, a negative rapid test is usually considered sufficient, and a backup culture isn’t routinely needed.
What Happens If Strep Goes Untreated
The reason strep testing exists at all comes down to prevention. Strep throat itself is uncomfortable but manageable. The real concern is what can follow if the infection isn’t treated with antibiotics. Rheumatic fever is the most serious complication: it’s an inflammatory condition that can damage the heart, joints, brain, and skin. If rheumatic fever develops and isn’t addressed promptly, it can progress to rheumatic heart disease, which weakens the heart’s valves and in severe cases requires surgery. Strep can also lead to kidney inflammation and peritonsillar abscesses. Antibiotics, started within the first few days of symptoms, effectively prevent these complications.
Getting Tested: Cost and Access
Strep tests are available at your primary care provider’s office, urgent care centers, retail clinics inside pharmacies, and emergency rooms. Urgent care is the most common choice for people seeking same-day testing. Without insurance, an urgent care visit runs roughly $125 to $300, with lab tests like a rapid strep adding anywhere from $10 to $225 depending on your location and the facility. Some urgent care centers in certain states bundle basic lab work into a flat consultation fee. With insurance, strep testing is typically covered as a standard diagnostic test, often subject to your copay.
Retail clinics (like those at CVS or Walgreens) tend to be less expensive than urgent care for straightforward complaints like sore throats, and many can run a rapid strep test on-site. If a culture is needed, the sample will be sent out, and results usually come back the next day by phone or patient portal.
Reading Your Results
A positive rapid test means strep bacteria were detected, and you’ll likely be prescribed antibiotics before leaving the office. Most people start feeling better within a day or two of starting treatment, though you should finish the full course.
A negative rapid test means the test didn’t find strep, but it doesn’t always rule it out entirely. If your provider ordered a backup culture, you may get a call in one to two days with updated results. If the culture also comes back negative, your sore throat is almost certainly viral, and the treatment is rest, fluids, and over-the-counter pain relief. If the culture turns positive, your provider will call to start you on antibiotics at that point.