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Epstein-Barr virus is usually diagnosed with blood tests.†Heterophile antibody levels (antibodies react to infectious organisms in the blood and create immunity)†indicate a current infection with EBV.†Antibody levels (called "titers") against the EBV virus reveal if there is a current or prior infection from the virus.

Blood tests usually shows an increase in the overall number of white blood cells.†Blood can also be†examined under a microscope†to determine whether there is an increased number of white blood cells called lympocytes. These white blood cells help fight viral infections, and an increased number of "atypical" lymphocytes usually indicates current infection with mononucleosis. Studies show that most people have been infected with EBV at some point in their lives, and most†have few or no symptoms of viral infection.

The doctor will rely on a combination of clinical and laboratory findings to diagnose mononucleosis. The doctor will ask about the course of illness and perform a physical exam.

The mono test is ordered if your doctor suspects that you have infectious mononucleosis, which causes fever, headache, swollen glands, tiredness, and malaise. Your physician may detect that you have an enlarged spleen or liver. The mono test is used to determine whether you have infectious mononucleosis. The test is rapid and easy to perform, but not 100% accurate. More testing may be needed to confirm†that the disease is mononucleosis and not another illness.

The test will not be positive until you have been infected for about two weeks. Other tests may need to be ordered if the heterophil antibodies are negative, but your doctor still suspects mononucleosis as the cause of your symptoms.

Other blood tests that are more specific to the EBV can be used to find early infection or to confirm mononucleosis. These tests include the IgM and IgG antibodies to the viral capsid antigen (VCA), which can be found early in the patientís blood when the disease is in the acute phase. VCA IgM is only present during the acute phase of the disease, but the IgG antibodies can be found later, during the patientís recovery.

What does the test result mean?

A positive result on the mono test, together with symptoms of mononucleosis, is the basis for a diagnosis of infectious mononucleosis. In addition to a positive reaction on the mono test, an infected person also has a higher white blood cell count, with a higher-than-usual number of†atypical lymphocytes. Heterophil antibodies decline after the fourth week of illness, and the mono test will become negative as the infection resolves.

A negative test result means that a person may not have mononucleosis or that it is too early in the illness to detect the antibodies. The test may need to be repeated if symptoms remain. Infants and young children do not make heterophil antibodies when infected with EBV, so more specific viral tests must be ordered to make the diagnosis.

In most cases, test results are reported as numerical values rather than as "high" or "low", "positive" or "negative", or "normal". In these instances, it is necessary to know the reference range for the particular test. However, reference ranges may vary by the patient's age, sex, as well as the instrumentation or kit used to perform the test. To learn the reference range for your test, consult your doctor or laboratorian.

Is there anything else I should know?

In young adults, an effective laboratory diagnosis can be made on a single blood sample during the acute phase of the disease with a mono test. By ordering the more extensive battery of EBV blood tests, the physician will be able to learn whether a person is susceptible to EBV, has had a recent infection, has had EBV infection in the past, or has a reactivated EBV infection.

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Date of Last Update: 07/27/12