Strep test, throat culture, Streptococcal screen
This test looks for the bacteria that cause strep throat. This condition causes a severe sore throat and makes it painful to swallow. It's important to detect and treat strep throat as soon as possible because it can progress to more serious illnesses, such as rheumatic fever.
The bacteria most likely to cause strep throat and bacterial sore throats in general are called Group A beta-hemolytic Streptococcus pyogenes (GABHS).
This test is a highly reliable way to diagnose strep throat because it has a sensitivity of 90% to 95%. But it's not used as commonly as the rapid antigen test because results for the throat culture are usually not available until 24 to 48 hours later.
You may need this test if you have symptoms of strep throat, including:
Sore throat. The soreness can begin suddenly and cause severe pain when you swallow.
Fever. Temperatures in adults are usually 101°F (38.3°C) or higher.
Headache, nausea, and vomiting
Mild neck stiffness
Swollen or enlarged lymph nodes in the neck
Swollen, red tonsils. Sometimes they have streaks of pus or white patches.
Rash or body aches
Small red spots on the roof of your mouth, in the back on the soft or hard palate
You may also have this test if your tonsils are painfully enlarged and your breath smells very bad.
Strep throat is treated with antibiotics. Starting antibiotics right away eases symptoms and can reduce the time you are contagious from 1 week to 1 day. Treatment also prevents rheumatic fever if taken within 10 days after symptoms begin.
Your healthcare provider may also order these tests:
Rapid antigen test
Clinical prognostic score for GABHS, a score that helps prevent overuse of antibiotics for sore throats
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your healthcare provider.
Normal results are negative, meaning you don't have strep throat. If your test result is positive, you almost certainly have strep throat caused by GABHS. If your sore throat lasts longer than a week, you probably have a different illness.
If your test is positive, you should stay home from work or school until you have been taking your antibiotics for 24 hours. It is important to do this so the infection won’t be spread to others. You should start feeling better within 1 to 2 days after starting the antibiotics.
Be sure to finish the entire prescription even though you are feeling better.
The test requires a sample from your throat. Your healthcare provider will take the sample by swabbing both of your tonsils.
The swabbing may cause a slight discomfort.
Taking antibiotics can affect your results.
You don't need to prepare for this test. But be sure your healthcare provider knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.