Strep Throat Testing

Throat Exam
Throat Exam. Pamela Moore/Getty Images

A strep test is the method used to diagnose strep throat. Strep throat is an infection caused by group A streptococcus pyogenes or GAS. There are two kinds of tests that can be used to detect strep throat.

Throat Culture

The throat culture is the gold standard when it comes to diagnosing strep throat. While this is always performed when testing for strep throat, your physician may also order a rapid strep test if there is a high enough suspicion for strep throat, as culture will take between 24 to 48 hours.

According to research, the majority of strep tests are negative, as there are many other causes for having a sore throat, and therefore the throat culture is more economical as well as the more accurate of the two types of tests available.

Rapid Antigen Detection Test

The rapid antigen test, better known as the rapid strep test, provides immediate results. However it is only accurate between 70-90% of the time. This means that 10-30% of the time, if you receive a negative rapid strep test result, the throat culture may come back positive. The rapid strep test however is very accurate when it comes back positive. Your doctor will not need to wait for the throat culture results in order to prescribe an antibiotic.

How Strep Tests Are Performed

Both the rapid strep test and a throat culture can cause a small amount of discomfort. The doctor will tell you to open your mouth as wide as possible.

While using a tongue depressor, the doctor will rub the back of your throat with a long cotton swab (often, specifically the tonsils). Occasionally, two swabs are necessary. This can cause a gagging sensation, but it is usually performed very quickly (within just a few seconds). The swabs are then evaluated for the streptococcus bacteria.

If the rapid strep test is positive, you (or your child) will be prescribed an antibiotic. If the rapid strep test comes back negative, most doctors will not give a prescription. However, if the throat culture comes back positive for strep later, your doctor will most likely call an antibiotic prescription into your pharmacy. Strep throat must be treated with an antibiotic to avoid long-term and dangerous strep complications — especially in children.


Wald, E.R. (2015). Approach to diagnosis of acute infectious pharyngitis in children and adolescents. Accessed on November 1, 2015 from

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