Mononucleosis Test

This test checks to see if you are infected with the virus that causes mononucleosis, or "mono."

This test checks to see if you are infected with the virus that causes mononucleosis, or "mono."

Mononucleosis, or "mono," is a viral infection. It is typically caused by the Epstein-Barr virus (EBV) or cytomegalovirus (CMV). When someone has mononucleosis, their body produces antibodies to fight the virus. Heterophile antibodies are made by the body in response to a mononucleosis infection. Although heterophile antibodies are common during a mono infection, they are not specific for the virus and do not actually fight the infection.

  • Most people with mono produce heterophile antibodies, which can be detected with a rapid screening mono test. This in-office test checks for the presence of heterophile antibodies in order to diagnose infectious mononucleosis.
  • Heterophile antibodies are not specific for EBV. Sometimes the test for heterophile antibodies is negative in a person with mono symptoms. In that case, a test specific for EBV antibodies may be performed.

The highest level of heterophile antibodies usually occurs within two to five weeks of infection. (They can remain in the blood for up to 1 year.) Therefore, this test is not usually used if symptoms have been present for longer than six months. Your healthcare provider may recommend another blood test to determine if you have an active infection.

In an adult, the blood sample is taken by placing a needle in a vein in the arm.

  • If this test is negative, it means there were no heterophile antibodies in your blood. This most likely means you do not have mononucleosis. However, if the test was done during the first couple of weeks of symptoms, a false negative result is possible. This is because your body has not had time to make the heterophile antibodies. Your healthcare provider may need to repeat the test.
  • If the test is positive, it means the heterophile antibodies were detected and you most likely have mononucleosis. However, the test may also be positive if you have had mononucleosis in the past, but do not have it now. Your healthcare provider will consider your symptoms and the results of other blood tests to determine if you have active mononucleosis.
  • A few people with mononucleosis will not have produce heterophile antibodies, so they will not have a positive test result. However, the test is generally very sensitive and will usually be positive if the virus that causes mononucleosis is present.
  • False positive tests are rare, but can happen in people with various medical conditions, including hepatitis, leukemia, rubella, lupus, and toxoplasmosis.

What should I ask my healthcare provider before having this test?

  • If the test is positive, what is my treatment plan?
  • If the test is positive, what precautions should I take?
  • If the test is negative, what else could be causing my symptoms?
  • What other tests might I need?


Also known as:

Swollen Spleen
Sore Throat
Mononucleosis Test
Laboratory Work
Kissing Disease
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