Tests and diagnosisBy 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)
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.
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