Diagnosis

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 also may 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 the clinic or 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 often return results within several hours or a couple of days.

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.