Strep Throat - Exams and Tests

Exams and Tests

Strep throat is diagnosed from your medical history, a physical examination of your throat, and a rapid strep test. A throat culture may sometimes be done to confirm the result of the rapid strep test or when your health professional suspects the rapid strep test result was inaccurate.

Current treatment guidelines recommend that your health professional confirm strep throat with a rapid strep test and not just diagnose strep throat from your symptoms.¹ However, your health professional may begin treatment for strep throat before the result of your throat culture is back if you have 3 or 4 of the following symptoms:¹

• A recent fever of 101° (38.3°) or higher
• White or yellow spots or coating on the throat or tonsils
• Swollen or tender lymph nodes on the neck
• Absence of signs of a cold or upper respiratory infection, such as coughing or sneezing

One or both of the following tests are used to confirm that you have strep throat.

• Rapid strep test analyzes the bacteria in your throat to see if strep is the cause of your sore throat. The health professional uses a cotton swab to gather cells from the back of your throat for testing.
• Throat culture is also a test that analyzes cells from the back of your throat. The cells are gathered with a cotton swab and then placed in a container with substances that promote the growth of strep bacteria. If the strep bacteria grow, the culture is positive; if not, the culture is negative.

If symptoms of strep throat are present, it is important to be tested for strep infection. Prompt treatment will reduce the spread of strep throat and may reduce the risk of complications, such as the infection spreading to other parts of your body causing ear or sinus infections or an abscess behind or around your tonsils (peritonsillar abscess).

If you need to be tested for strep throat, the choice between a rapid strep test and a throat culture may not be clear. It may be helpful to discuss with your health professional the advantages and disadvantages of each test. For instance, results from a rapid strep test are available within 10 to 15 minutes, while results from a throat culture may take 1 to 2 days. However, a throat culture is more accurate.

• A negative rapid strep test result can mean there are no strep bacteria present. However, the rapid strep test can give negative results even when strep bacteria are present (false-negative test results). If the rapid strep test result is negative but strep throat is still suspected, your health professional may order a throat culture to verify the results.
• If the rapid strep test result is positive, a throat culture is not needed. Antibiotic treatment can be started right away, reducing the length of time (by about 8 hours) that you are sick and contagious.

Testing is not needed:

• After antibiotic treatment, unless you still have symptoms. Testing may be done if symptoms return or you have had rheumatic fever and are at risk for it coming back.²
• For a person who was exposed to strep but has no symptoms. For instance, family members of a person who has strep throat do not need to be tested unless they start to have symptoms.

It is possible for a person to carry the strep bacteria and not have any symptoms.³ If a number of infections occur in the same family, or if there have been severe complications such as rheumatic fever or toxic shock syndrome, it may be beneficial to test family members to learn whether they are carriers of strep infection. However, it is unusual for a person to catch strep throat from a carrier.