Health Guide

Microbial identification kit, rapid strep method

What is this test?

This test is done to quickly check for bacteria in the throat. This test is done to identify and manage a group A beta-hemolytic streptococcal infection (strep throat) [1][2][3][4][5].

What are other names for this test?

  • Streptococcus screening test, direct

What are related tests?

Why do I need this test?

Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:

  • Strep throat

When and how often should I have this test?

When and how often laboratory tests are done may depend on many factors. The timing of laboratory tests may rely on the results or completion of other tests, procedures, or treatments. Lab tests may be performed immediately in an emergency, or tests may be delayed as a condition is treated or monitored. A test may be suggested or become necessary when certain signs or symptoms appear.

Due to changes in the way your body naturally functions through the course of a day, lab tests may need to be performed at a certain time of day. If you have prepared for a test by changing your food or fluid intake, lab tests may be timed in accordance with those changes. Timing of tests may be based on increased and decreased levels of medications, drugs or other substances in the body.

The age or gender of the person being tested may affect when and how often a lab test is required. Chronic or progressive conditions may need ongoing monitoring through the use of lab tests. Conditions that worsen and improve may also need frequent monitoring. Certain tests may be repeated to obtain a series of results, or tests may need to be repeated to confirm or disprove results. Timing and frequency of lab tests may vary if they are performed for professional or legal reasons.

How should I get ready for the test?

There is no preparation needed for this test.

How is the test done?

A throat culture is done to collect mucus and cells from the back of your throat. For a throat culture, you will need to open your mouth wide. The person doing the test will use a long, sterile cotton swab to swab the back of your throat, near your tonsils. The swab may be rubbed several times to obtain the sample. Do not close your mouth when the sample is being collected. After the sample has been collected, the swab will be taken out and tested.

How will the test feel?

The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.

During a throat culture, you may feel mild discomfort at the back of your throat when the sample is collected. You may feel like gagging or coughing. You may have a mild sore throat briefly after the procedure.

What should I do after the test?

There are no special instructions to follow after this test.

What are the risks?

Ask the healthcare worker to explain the risks of this test or procedure to you before it is performed.

What are normal results for this test?

Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a disease. Contact your healthcare worker if you have any questions. The following is considered to be a normal result for this test:

  • Negative for group A streptococcal carbohydrate [6][7]

What follow up should I do after this test?

Ask your healthcare worker how you will be informed of the test results. You may be asked to call for results, schedule an appointment to discuss results, or notified of results by mail. Follow up care varies depending on many factors related to your test. Sometimes there is no follow up after you have been notified of test results. At other times follow up may be suggested or necessary. Some examples of follow up care include changes to medication or treatment plans, referral to a specialist, more or less frequent monitoring, and additional tests or procedures. Talk with your healthcare worker about any concerns or questions you have regarding follow up care or instructions.


[1] Edmonson MB & Farwell KR: Relationship between the clinical likelihood of group a streptococcal pharyngitis and the sensitivity of a rapid antigen-detection test in a pediatric practice. Pediatrics 2005; 115(2):280-285.

[2] Lindbaek M, Hoiby EA, Lermark G, et al: Which is the best method to trace group A streptococci in sore throat patients: culture or GAS antigen test. Scand J Prim Health Care 2004; 22(4):233-238.

[3] Gerber MA & Shulman ST: Rapid diagnosis of pharyngitis caused by group A streptococci. Clin Microbiol Rev 2004; 17(3):571-580.

[4] Corneli HM: Rapid strep tests in the emergency department: an evidence-based approach. Pediatr Emerg Care 2001; 17(4):272-278.

[5] Heiter BJ & Bourbeau PP: Comparison of two rapid streptococcal antigen detection assays with culture for diagnosis of streptococcal pharyngitis. J Clin Microbiol 1995; 33(5):1408-1410.

[6] Alcaide ML & Bisno AL: Pharyngitis and epiglottitis. Infect Dis Clin North Am 2007; 21(2):449-69, vii.

[7] Bisno AL, Gerber MA, Gwaltney JM, et al: Practice guidelines for the diagnosis and management of group A streptococcal; pharyngitis. CID 2002; 35:113-125.

Last Updated: 7/4/2018
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