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Strep Throat Test

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Also known as: Throat Culture; Culture, Throat; Rapid Strep Test; Rapid Antigen Detection Test; RADT; Streptococcal Screen
Formal name: Group A streptococcus (GAS); Group A beta hemolytic streptococcus

The Test Sample

What is being tested?

The bacteria Streptococcus pyogenes, also known as group A beta-hemolytic streptococcus or group A streptococcus (GAS), causes "strep throat," the most common bacterial cause of inflammation and soreness of the back of the throat (pharyngitis). Strep throat tests identify the presence of these bacteria as the cause of a sore throat.

While most sore throats are caused by a virus and will resolve without treatment within a few days, some people with sore throats have strep throat. Strep throat is most common in children ages 5 to 15 years old. It is important that these bacterial strep infections be promptly identified and treated with antibiotics.

Strep throat is contagious and can spread when an infected person coughs or sneezes and other people come into contact with the droplets or mucus. Touching the face, eyes or mouth after touching something that has these droplets on it can spread the infection. The best way to avoid getting strep throat is to wash hands thoroughly and often and avoid sharing items like utensils or cups. A person who has a sore throat should wash their hands often and cover their mouth with a tissue or sleeve when coughing and sneezing.

If strep throat is not diagnosed and treated, secondary complications may develop, especially in children. These complications may include rheumatic fever, which can damage the heart, and glomerulonephritis, which affects the kidneys. Because streptococcal infections are routinely diagnosed and treated, these complications are rare in the United States now, but they do still occur.

A rapid strep test and/or a throat culture is used to diagnose group A streptococci as the cause of symptoms and allows the health practitioner to prescribe the proper antibiotics for treatment. (Read more on the "The Test" tab.)

How is the sample collected for testing?

A health practitioner uses a tongue depressor to hold down a person's tongue and then inserts a special swab into the mouth and rubs it against the back of the throat and tonsils. The swab may be used to do a rapid strep test in a doctor's office or clinic, or it may be sent to a laboratory. A second swab may be collected along with the first one. This extra sample is used to perform a throat culture as a follow-up test, when necessary.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed. The test should be performed before antibiotics are prescribed.