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The monospot test is used to diagnose glandular fever (infectious mononucleosis) by detecting the antibodies your body makes to the Epstein-Barr virus (EBV) which causes the infection. It is used as an initial screen because only 70 to 80 percent of cases of glandular fever produce antibodies.

If the test is negative (most commonly in young children) and the symptoms persist, your doctor may arrange for more specific tests for EBV infection or test for other possible infections.

What is being tested?

The Monospot test detects heterophile antibodies. "Heterophile" antibodies are antibodies that react with the cells of other species of animals. The antibodies are made in response to an infection such as by Epstein-Barr virus (EBV) and, much less commonly, in response to some other viral infections, autoimmune diseases and non-infectious conditions.


EBV causes infectious mononucleosis (glandular fever), a self-limiting disease.
Infectious mononucleosis is characterised by the presence of unusual white blood cells (atypical lymphocytes) in an infected person. Patients generally have symptoms of: fever, sore throat, swollen glands, and fatigue. About 70% - 80% of patients with infectious mononucleosis produce heterophile antibodies. The test may be negative in young children with EBV infections.

How is it used?

The infectious mononucleosis (IM) screening test is used to determine whether you have infectious mononucleosis. This test is rapid and easy to perform (results should be available after 1 day). The results will be either positive or negative for heterophile antibodies, however, it is not 100%  specific for infectious mononucleosis. More testing may be needed to confirm  infectious mononucleosis and ensure symptoms are not caused by another illness.

When is it requested?

The IM screening test is requested if your doctor suspects that you have infectious mononucleosis, which causes fever, headache, swollen glands, tiredness, and malaise. Your doctor may also detect that you have an enlarged spleen or liver.

The test will not be positive until you have been infected for approximately two weeks or longer. Other tests may need to be requested if the heterophile antibodies are negative but your doctor still suspects mononucleosis as the cause of your symptoms.


Blood tests specific for EBV infection can be used to find early infection or to confirm mononucleosis. These tests include the IgM and IgG antibodies to the EBV viral capsid antigen (VCA), which can be found early in the disease. VCA IgM is only present early, but IgG antibodies can also be found later, during the patient's recovery.a

What does the result mean?

A positive result in the IM screening test, together with symptoms of mononucleosis, is the basis for a diagnosis of infectious mononucleosis. In addition to a positive reaction on the IM screening test, an infected person generally has an increased white blood cell count, with a higher than usual number of lymphocytes which may appear reactive. Heterophile antibodies decline after the fourth week of illness, and the 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 often do not make heterophile antibodies when infected with EBV, so more specific viral tests must be used to make the diagnosis.

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 (initial) phase of the disease with an IM screening test for heterophile antibodies. By requesting the more extensive battery of EBV blood tests, the doctor will be able to learn whether a person is susceptible to EBV, has had a recent infection, has had an EBV infection in the past, or has a reactivated EBV infection.


When the IM screening test is negative, a combination of EBV antibody tests for IgM and IgG to the viral capsid antigen, IgM to the early antigen, and IgG antibody to the nuclear antigen may be requested.

Common questions

  • How serious is infectious mononucleosis?

Fever and soar throat usually resolve spontaneously within 2-3 weeks. Sometimes your spleen or liver may enlarge, and you may have to limit your activity until these organs return to normal size (e.g., you may be told to avoid contact sports while your spleen is enlarged). Heart problems or involvement of the central nervous system occur only rarely.


  • Is mononucleosis really a "kissing disease"?

Glandular fever mostly affects teenagers to young adults and spread through  close contact with saliva of an infected person. Kissing can transmit infection, but saliva on toys or hands can also transmit the virus. An infected person should avoid kissing others, sharing drink containers and regularly wash their hands.

Transmission through the air or blood does not normally occur. The incubation period, the time from infection to appearance of symptoms, ranges from 4 to 6 weeks.

People who have infectious mononucleosis may be able to spread the infection to others for a period of weeks. Many healthy people can carry and spread the virus intermittently for life, without any symptoms, and testing them for the virus is not practicable. For this reason, it is almost impossible to prevent the virus spreading in the community.


  • Does the Epstein-Barr virus cause chronic fatigue syndrome?

There is no laboratory evidence indicating that EBV infection causes chronic fatigue. For more information, visit the Centres for Disease Control and Prevention’s chronic fatigue website.


  • Can I get infectious mononucleosis more than once?

Although the symptoms of infectious mononucleosis usually go away in 1 or 2 months, EBV remains inactive in a few cells in the body for the rest of the person's life. Periodically, the virus can reactivate, and it is commonly found in the saliva of infected persons. This reactivation usually occurs without symptoms of illness.


  • Can EBV cause other serious illnesses?

Rarely, EBV has been linked to more serious illnesses such as haemophagocytic lymphohistiocytosis (HLH) and lymphoproliferative disorders such as Burkitt’s lymphoma, Hodgkin’s disease, nasopharyngeal carcinoma, and AIDS-related lymphoma. It continues to be studied for possible linkages to these and other cancers. All these diseases are rare.

Last Updated: Thursday, 1st June 2023

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