WEDNESDAY, Jan. 17 (HealthDay News) -- A common blood test that measures a patient's ratio of white blood cell types can help doctors distinguish between tonsillitis and mononucleosis and provide appropriate treatment, British researchers say.

Tonsillitis and mononucleosis are common conditions with similar symptoms, including sore throat, fever, painful swallowing, redness of the throat and tonsils, and white plaque on the tonsils, according to background information in the study.

"The importance of differentiating patients with tonsillitis from those with glandular fever (mononucleosis) is the prevention of spontaneous rupture of the spleen and acute intra-abdominal hemorrhage," both of which are potential complications of mononucleosis, the researchers wrote.

Currently, an expensive mononucleosis spot test is required to differentiate between the two conditions.

In this study, the researchers analyzed laboratory test results from 100 patients with bacterial tonsillitis and 120 patients with infectious mononucleosis. They looked at the number of lymphocytes (a type of white blood cell involved in immune response) and overall white blood cell count, and found the lymphocyte/white blood cell count ratio averaged 0.54 in the mononucleosis patients and 0.10 in tonsillitis patients.

The study authors concluded that people with a ratio of higher than 0.35 would be correctly diagnosed with mononucleosis 90 percent of the time and people with a ratio of 0.35 or lower would be correctly diagnosed as not having mononucleosis 100 percent of the time.

"In conclusion, we recommend that the lymphocyte-white blood cell count ratio should be used as an indicator to decide whether mononucleosis spot tests are required," the study authors wrote. "Results from our retrospective pilot study suggest that the lymphocyte-white blood cell count ratio could be quickly available alternative test for the detection of glandular fever (mononucleosis)."

The study is published in the January issue of the Archives of Otolaryngology-Head & Neck Surgery.

More information

The American Academy of Family Physicians has more about mononucleosis.