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Mononucleosis Tests

Results

Mononucleosis tests are blood tests to look for antibodies that indicate mononucleosis (mono), which is usually caused by the Epstein-Barr virus (EBV). The antibodies are made by the immune system to fight an infection.

Monospot test

The results of a monospot test are usually ready within 1 hour.

Monospot test
Normal (negative):

The blood sample does not form clumps (no heterophil antibodies are detected).

Abnormal (positive):

The blood sample clumps (heterophil antibodies are detected). If the blood sample clumps, you probably have mono.

Epstein-Barr antibody testing

The results of the antibody test to detect Epstein-Barr virus (EBV) may be reported as positive (antibodies are present) or negative (antibodies are not present). Or the test results may be reported in titers.

The EBV antibody test can also detect the type of antibodies (immunoglobulins) present in the blood. The type of antibody shows whether the infection is recent or old. The antibody IgM is only found during the active phase of mono. The antibody IgG can be found later, when you are starting to get better.

The results of an EBV antibody test are usually ready within 3 days.

EBV antibody test 1
Normal (negative):

The titer is less than 1 to 10 (1:10). A titer of less than 1:10 means that you have never been exposed to EBV.

No IgM against EBV is present. If IgG is present, it may mean that you have been exposed to EBV in the past.

Abnormal (positive):

A titer greater than 1 to 10 (1:10) but less than 1:320 usually means that you have been infected with EBV at some time in the past.

A titer of 1:320 or greater means that you have an active EBV infection (mononucleosis).

IgM against EBV is present.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Having an EBV antibody test within the first few weeks of becoming infected with EBV. This may lead to a false-negative result. If the first test does not indicate mono but you still have symptoms, the test may be repeated.
  • Other infection or disease, such as cytomegalovirus (CMV), leukemia or lymphoma, rubella, hepatitis, or lupus. Although the symptoms of these infections and diseases are similar to mono, the monospot test usually will be negative.
  • Having a weakened immune system.

WebMD Medical Reference from Healthwise

Last Updated: July 22, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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