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People who have a sore throat without a runny nose that lasts for more than 48 hours are urged to consult a physician. The physician will perform a physical examination that will likely include a visual inspection of the throat. A tongue depressor may be used to enable clear viewing of the back of the throat. A medical history may be compiled, which can include questions about the frequency of the patient’s throat infections. The patient may also be referred to an ear, nose and throat specialist.

Strep throat cannot be diagnosed strictly by symptoms and physical examination. The only way to identify the presence of strep throat is through the following diagnostic tests:

• Rapid strep test (also called the rapid antigen test). A physician will swab the surface of the tonsils, located at the back of the patient’s throat for a tissue sample. This can be analyzed and results are typically available within about 15 minutes. It can detect the strep bacteria in 75 percent to 85 percent of strep throat cases, according to the American Academy of Family Physicians (AAFP).
  
  
• Throat culture. A physician swabs the patient’s tonsils(similar to the method used for the rapid strep test) and the tissue sample is then sent to a laboratory for analysis. Results are generally not available for at least a day or two.

Generally, both tests are performed, particularly if the rapid strep test is negative. The rapid strep test allows treatment to begin immediately (if strep throat is detected) and the throat culture is used to confirm this result. Occasionally, the throat culture (a more sensitive test) may detect a strep throat infection that was missed during the rapid strep test. It should be noted that recent antibiotic therapy or gargling with some types of mouthwash prior to these tests may affect results.

A new diagnostic test has been developed that uses DNA technology, called the rapid DNA test. It provides results within a few hours, and may be more sensitive than the rapid antigen test. Patients are urged to consult with the physician about the availability of this test.

Family members who are not currently displaying symptoms of strep throat will sometimes receive a rapid strep test and throat culture to help determine if they are carriers.

It is important to note that strep tests and cultures sometimes miss a number of other types of conditions that also cause severe sore throats. These include severe tonsillitis or tonsillar abscess, diphtheria, and infections of the throat resulting from oral sex. The presence of bacteria growing in the blood (septicemia) can also cause symptoms similar to strep. As a result, further testing may be necessary to rule out these conditions in patients who have sore throats but who test negatively for strep.