Tests and diagnosis

By Mayo Clinic Staff

Your child's doctor will start with a physical exam that will include:

  • Using a lighted instrument to look at your child's throat and likely his or her ears and nose, which may also be sites of infection
  • Checking for a rash known as scarlatina, which is associated with some cases of strep throat
  • Gently feeling (palpating) your child's neck to check for swollen glands (lymph nodes)
  • Listening to his or her breathing with a stethoscope
  • Checking for enlargement of the spleen (for consideration of mononucleosis which also inflames the tonsils)

Throat swab

With this simple test, the doctor rubs a sterile swab over the back of your child's throat to get a sample of secretions. The sample will be checked in a lab for streptococcal bacteria.

Many clinics are equipped with a lab that can get a test result within a few minutes. However, a second more reliable test is usually sent out to a lab that can return results within 24 to 48 hours.

If the rapid in-clinic test comes back positive, then your child almost certainly has a bacterial infection. If the test comes back negative, then your child likely has a viral infection. Your doctor will wait, however, for the more reliable out-of-clinic lab test to determine the cause of the infection.

Complete blood cell count (CBC)

Your doctor may order a CBC with a small sample of your child's blood. The result of this test, which can often be completed in a clinic, produces a count of the different types of blood cells. The profile of what's elevated, what's normal or what's below normal can indicate whether an infection is more likely caused by a bacterial or viral agent. A CBC is not often needed to diagnose strep throat. However, if the strep throat lab test is negative, the CBC may be needed to help determine the cause of tonsillitis.

Aug. 04, 2012