Strep Test

This test identifies the presence of the bacteria Streptococcus pyogenes, also known as group A beta-hemolytic streptococcus and group A streptococcus (GAS). Group A streptococci can infect the back of the throat and cause “strep throat,” the most common bacterial cause of inflammation and soreness of the back of the throat (pharyngitis).

While most sore throats are caused by a virus and will resolve without treatment within a few days, 5-15% of adults and 15-30% of children have bacterial infections caused by this bacteria. It is important that these strep infections be promptly identified and treated with antibiotics. Strep throat is contagious and can spread to close contacts. If the infection is not treated, secondary complications may develop, such as rheumatic fever, which can damage the heart, and glomerulonephritis, which affects the kidneys. Because streptococcal infections are routinely diagnosed and treated, these complications have become much rarer in the United States, but they do still occur.

Symptoms of strep throat vary and can be similar to those caused by other infections. They may include:

• Sore throat
• Fever
• Headache
• Reddened (inflamed) throat with or without white or yellow spots
• A swollen, tender neck
• Weakness
• Loss of appetite

A rapid strep test and/or a throat culture is used to diagnose group A streptococci as the cause of these symptoms and allows the doctor to prescribe the proper antibiotics for treatment.

A doctor, nurse, or other health care professional uses a tongue depressor to hold down your tongue and then inserts a special swab into your 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.

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