How is it used?
A rapid strep test is used to determine whether a person with a sore throat (pharyngitis) has a group A streptococcal infection.
If the results of the rapid test, which takes 10 - 20 minutes, are positive, further testing is not needed. If the rapid strep test is negative, a throat culture should be performed to grow the bacteria in the laboratory and confirm the results. A throat culture is more accurate than the rapid strep test, but it may take several days to get results.
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When is it ordered?
A doctor will typically order this test when a person has a sore throat and other symptoms that suggest strep throat. He will have a higher suspicion of strep when the affected person is a child and/or if the person has been in close contact with someone who has been diagnosed with strep throat. Symptoms of strep throat vary and may include:
- sore throat
- fever
- headache
- reddened (inflamed) throat with or without white or yellow spots
- a swollen, tender neck
- weakness
- loss of appetite
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What does the test result mean?
A positive rapid strep test indicates the presence of group A streptococci, the
bacteria that cause strep throat. A negative rapid test indicates that the affected person probably does not have strep throat, but the possibility cannot be ruled out until the laboratory performs a throat culture. If the throat culture is positive for group A streptococci, then the person tested does have strep throat. If it is negative, then it is most likely that the sore throat is due to a
viral infection that will resolve on its own.
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Is there anything else I should know?
Strep throat spreads from person-to-person through contact with respiratory secretions that contain the streptococcal bacteria. During influenza season, the early symptoms of influenza, such as fever, chills, headache, sore throat, muscle pain, may mimic strep throat. Very rarely, these same symptoms may be due to a more serious acute illness,
septicemia. To differentiate between strep and influenza, a rapid strep test and a rapid
influenza test may both be done. If both tests are negative and the clinical signs warrant it, a
complete blood count (CBC) may be ordered to evaluate the person's white blood cells and, rarely,
blood cultures may be drawn to rule out
sepsis. The treatment for each of these infections differs greatly and making a prompt diagnosis is imperative to starting the correct therapy.
Most people with streptococcal pharyngitis would eventually recover without antibiotic treatment, but they will be contagious for a longer period of time and are at a greater risk of developing secondary complications.
Strep throat is most common in 5- to 10- year olds. Up to 20% of school children may be "carriers," persons who have the bacteria but who have no symptoms. Carriers can still spread the infection to others.
Recent antibiotic therapy or gargling with some mouthwashes may affect the rapid strep test results.
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