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Parents who suspect their child may have tonsillitis should consult their child’s pediatrician. They may be referred to an ear, nose and throat specialist (otolaryngologist) for examination.

A medical history is usually gathered, and may include questions about the frequency of throat or other upper respiratory tract infections in the child.

A physical examination will include a visual examination of the throat to check for redness, swelling or pus on the tonsils. A physician may use a tongue depressor to hold the tongue down. In addition, a child may be asked to say “ahhhh,” which can keep the tongue flattened enough to enable a view of the back of the throat. The ears and nose may also be examined for other signs of infection. A physician may also listen to the child’s chest.   

Diagnosis of tonsillitis may be made based on the physical examination. However, there is no way to identify the cause of infection (e.g., whether viral or bacterial) by visual inspection alone. It is important to identify bacterial infections because they require antibiotic treatment.

Bacterial infections may be identified with several different tests, including a throat culture and a strep screen. For a throat culture, a physician uses a long cotton swab to obtain a tissue sample from the back of the child’s throat. Although painless, throat cultures may cause a child to momentarily gag. Results are not usually available for a day or two. A rapid strep test is performed in a similar manner, but results are available within minutes. This test is usually performed in conjunction with the throat culture. If these tests are negative, the tonsillitis may be caused by a virus. However, negative results from a rapid strep test are normally confirmed with the full strep screen test, to avoid missing any bacterial infections.

In cases where the suspected cause of tonsillitis is the Epstein-Barr virus (the virus that causes mononucleosis), a special blood test called the mononucleosis spot test (or monospot test) may be performed.

However, a regular – and more cost effective – blood test measuring the number of lymphocytes (a particular type of white blood cell involved in the body’s immune system response to infection) and overall white blood cell count can help distinguish between tonsillitis caused by bacterial infection or by the viral infection mononucleosis, according to a new study published in the Archives of Otolaryngology – Head & Neck Surgery. The research team recommends the lymphocyte-white blood cell count ratio as an indicator for physicians to determine whether the mononucleosis spot test is necessary. A ratio higher than 0.35 can confirm or rule out mononucleosis.