To determine if a sore throat is "strep throat" that is caused by group A streptococcus (GAS)
Strep Test
Strep Test
Também conhecido como
Throat culture
Culture, throat
Rapid strep test
Nome formal
Group A streptococcus; Group A beta hemolytic streptococcus
Este artigo foi revisto pela última vez em
Este artigo foi modificado pela última vez em 10 de Julho de 2017.
At a Glance
Why Get Tested?
When To Get Tested?
When you have a sore throat that your doctor thinks may be due to a bacterial infection
Sample Required?
A swab rubbed against the back of your throat and tonsils
Test Preparation Needed?
None
Accordion Title
Common Questions
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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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How long does treatment for strep throat usually last?Ten to 14 days, depending on the antibiotic prescribed.
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How long should I stay away from other people if I have a positive test result?You should complete at least 24 hours of antibiotics before close contact with others.
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When can my child go back to school?Usually after one full day of therapy and absence of significant fever.
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If one child in my family has strep throat, is everyone going to get sick?Other family members, including adults, can be infected by the bacteria. The doctor will usually test all family members who have sore throats and may, in some instances, want to test the whole family for strep throat. Although antibodies may protect those who have had previous strep infections, there are so many different strains of this organism that being immune to all of them is unlikely. Therefore, someone could potentially get strep throat again and again. The best way to decrease the risk of transmission of the bacteria to others is to cover coughs and sneezes by coughing and/or sneezing into the bend of your arm or shoulder. After sneezing or coughing into a tissue or handkerchief, wash hands thoroughly with soap and water or alcohol-based hand scrub.
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What is an ASO test and how is it used to detect a strep infection?Antistreptolysin O (ASO) is a blood test used to help diagnose a current or past infection with group A strep (Streptococcus pyogenes). It detects antibodies to streptolysin O, one of the many strep antigens. This test is rarely ordered now compared to thirty years ago. For an acute strep throat infection, the ASO test is not helpful; the rapid strep test or throat culture should be used. However, if a doctor is trying to find out if someone had a recent strep infection that may not have been diagnosed, this test could be helpful. In addition, it may be used to help diagnose rheumatic fever or glomerulonephritis, which occurs weeks after a strep throat infection when the rapid strep and throat culture would no longer be positive.
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Do other group A streptococous infections occur?Group A streptococcus can also cause infections that occur separately from strep throat, such as impetigo and, rarely, more invasive conditions such as toxic shock syndrome or necrotizing fasciitis (the so-called “flesh-eating bacteria”).