Diagnosis of glandular fever is primarily based on history of signs and symptoms of the infection, physical examination and is confirmed by blood tests. Diagnosis is preceded by taking a detailed history.
Age of patient with glandular fever
The age of the patient is usually between 15 and 24.
However, people of all ages including children, elderly and pregnant women may acquire glandular fever.
There may be a history of exposure to a person with glandular fever or with Epstein Barr virus infection.
History taking is followed by a detailed physical examination. The physician detects classical features like an inflamed throat, swollen lymph nodes and tonsils and enlarged spleen and liver.
Blood tests for glandular fever
Blood tests to detect glandular fever include different types of antibody tests. (1-5)
An antibody test
The Epstein-Barr virus causes the body’s immune system to release certain proteins that gear up to fight against the virus. These are called antibodies. These antibodies can be detected through testing.
Antibody tests are usually positive during the phase where glands are enlarged. Initially during the fever and sore throat phase of the infection the antibody test may be negative. If glandular fever is suspected then the test should be repeated after the glands are swollen.
Heterophile antibody test
An antibody test may be directed towards heterophile antibodies. These are antibodies are basically proteins that react not only to EBV but to other proteins and invading germs as well.
Patients with infectious mononeucleosis commonly (85-90%) have heterophile antibodies.
These can be detected by the Paul-Bunnell test. This test uses sheep red blood cells that are specially prepared. These clump or aggregate when they are put in blood samples of patients with heterophile antibodies.
A similar test is a Monospot® test. Here horse red blood cells aggregate or agglutinate when exposed to heterophile antibodies.
During the initial six weeks of the disease, chances of a negative result are high as there are more specific antibodies.
The results may be falsely negative in 25% cases in the first week, 5-10% cases in second week and 5% cases in the third week of illness.
Results may be falsely negative in children less than 12 years of age and in the elderly.
The levels of these heterophile antibodies may remain in the body for up to one year.
Toxoplasmosis, rubella, cytomegalovisrus, HIV, malaria, viral hepatitis and herpes simplex also give positive results to these tests. Some blood cancers like lymphomas and rheumatoid arthritis also give positive results to these tests.
Specific antibodies for EBV
If results for heterophile antibodies are negative up to six weeks into the disease, EBV specific antibodies need to be tested. This also rules out other conditions that yield a positive result for heterophile antibodies.
The antibodies tested are developed by the body against proteins that lie within the core of the EB virus. These are called the antibodies against viral capsid antigens (VCAs) and the EBV nuclear antigen (EBNA). A test called ELISA is applied to check for these antibodies.
Antibodies to EBNA are not detectable until six to eight weeks after the onset of the disease. There may be cross reaction and falsely positive results with other herpes viruses. Young children less than two years may show negative results to this test falsely.
Routine blood test
Routine blood cell counts help to detect the presence of an infection. White blood cell counts are raised. There may be 15,000 to 20,000 WBCs per cm3 and 75% of these may be polynuclear cells.
This blood picture may be a transient feature and changes during the course of the disease. There may be a rise in mononuclear WBCs as the disease progresses.
Mononuclear WBCs are monocytes and lymphocytes. This is the reason why glandular fever is called infectious mononucleosis. The percentage of mononuclear cells are between 60 and 70% when the disease is fully developed.
Tests for other viruses
Tests for other viruses that cause glandular fever include those for rubella, cytomegalovirus and toxoplasma. A Toxoplasma screening test is important especially in pregnant women.
Liver function tests
Other tests include liver function tests to assess the liver health. An abdominal ultrasound may be advised to check for enlarged spleen or liver.