Rapid strep test
A streptococcal screen is a test to detect group A streptococcus. This type of bacteria is the most common cause of strep throat.
Sometimes when you have a sore throat, it's more than just a normal cold, especially if your throat feels raw or like it's on fire. Most people get sore throats from a viral infection, in other words, the common cold. But, occasionally, you might come down with strep throat, which is caused by a type of bacteria called Streptococcus pyogenes. These bacteria are contagious. Like with germs that cause a cold, you can also get strep throat from handling a doorknob or other surface, then touching your nose or mouth. How do you know for sure that you have strep throat? You may start to feel sick a few days after you come into contact with the bacteria that causes strep throat, but usually people will start feeling sick suddenly. You will probably have a fever very quickly, and your throat will be very sore. If you look in a mirror, the back of your throat may be very red, and you might see white patches on your tonsils. You may also have a headache, be sick to your stomach, and feel chills. Your doctor will check your throat for redness, swelling, and white patches, then rub a sterile swab over your tonsils, taking a sample of mucous. A rapid antigen test done at your doctor's office can find bacteria from the swab in minutes, so you can find out if strep throat is causing your symptoms. Your doctor will probably send the swab to a laboratory to double check your diagnosis, but this test may take a day or two. There's another common type of bacteria that can cause throat infections, especially in young adults; The bacteria's name is Fusobacterium necrophorum. I call it F-throat. Antibiotics are important for F-throat. It doesn't show up on strep tests, so it's important to keep in mind with severe sore throats or sore throats that aren't getting better as expected. Since strep does NOT cause most sore throats, your doctor will make sure you have it before treating you for it. If you do, your doctor will most likely ask you to take penicillin or amoxicillin for 10 days, even though you might feel much better after a few days. The reason is because strep throat can sometimes lead to more serious health problems, such as rheumatic fever. Be sure to tell your doctor if you're allergic to some antibiotics, so you can receive a different medication. While you wait for the antibiotics to start fighting the infection, you can follow these tips to help your throat feel better; Drink warm liquids like tea with honey; Gargle several times a day with a teaspoon of salt in a cup of warm water; Drink cold liquids, or suck on popsicles, hard candies, or throat lozenges; Keep a vaporizer or humidifier running in your room to soothe the dryness in your throat AND Take over-the-counter pain medicines. It's important to see your doctor if you think you have strep throat, because, untreated, it can lead to very serious health problems. Once you start treatment, your symptoms will probably be gone in about a week. But if you don't start feeling in a day or two, make sure you call your doctor.
How the Test is Performed
The test requires a throat swab. The swab is tested to identify group A streptococcus. It takes about 7 minutes to get the results.
How to Prepare for the Test
There is no special preparation. Tell your health care provider if you are taking antibiotics, or have recently taken them.
How the Test will Feel
The back of your throat will be swabbed in the area of your tonsils. This may make you gag.
Why the Test is Performed
Your provider may recommend this test if you have signs of strep throat, which include:
- Sore throat
- Tender and swollen glands at the front of your neck
- White or yellow spots on your tonsils
A negative strep screen most often means group A streptococcus is not present. It is unlikely that you have strep throat.
If your provider still thinks that you may have strep throat, a throat culture will be done in children and adolescents.
What Abnormal Results Mean
A positive strep screen most often means group A streptococcus is present, and confirms that you have strep throat.
Sometimes, the test may be positive even if you do not have strep. This is called a false-positive result.
There are no risks.
This test screens for the group A streptococcus bacteria only. It will not detect other causes of sore throat.
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Stevens DL, Bryant AE, Hagman MM. Nonpneumococcal streptococcal infections and rheumatic fever. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 274.
Tanz RR. Acute pharyngitis. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 409.
Last reviewed on: 1/23/2020
Reviewed by: Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.