Monospot Test

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Also known as: Mononucleosis spot test; mononuclear heterophil test; heterophil antibody test; Mono test
Formal name: Heterophil antibody titre
Related tests: Tests for antibodies to Epstein-Barr virus (EBV) antigens, Paul-Bunnell test

At a Glance

Why Get Tested?

To get screened for infectious mononucleosis (glandular fever)

When to Get Tested?

If you have symptoms of mononucleosis, including fever, sore throat, swollen glands, and fatigue

Sample Required?

A blood sample taken from a vein in your arm

The Test Sample

What is being tested?

The Monospot test detects heterophil antibodies, antibodies which react with the cells of other species. Monospot detects reaction with horse red blood cells, and a similar test, the Paul-Bunnell test, detects reaction with sheep red cells. The antibodies are made in response to an infection by Epstein-Barr virus (EBV). EBV causes infectious mononucleosis (glandular fever), a self-limiting disease.

Mononucleosis is characterized by the presence of atypical white blood cells (atypical lymphocytes) in an infected person. Patients have these symptoms: fever, sore throat, swollen glands, and fatigue. About 70%–80% of patients with infectious mononucleosis produce these heterophil antibodies, which are not specific for EBV infection but are a good predictor of EBV infection.

How is the sample collected for testing?

A blood sample is taken by needle from a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

The Test

How is it used?

The Monospot test is used to determine whether you have infectious mononucleosis. This test is rapid and easy to perform, but it is not 100% accurate. More testing may be needed to confirm that the disease is mononucleosis and not another illness.

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When is it requested?

The Monospot test is requested 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 test will not be positive until you have been infected for about two weeks. Other tests may need to be requested 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 disease. VCA IgM is only present early, but the IgG antibodies can also be found later, during the patient's recovery.

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What does the test result mean?

A positive result in the Monospot test, together with symptoms of mononucleosis, are the basis for a diagnosis of infectious mononucleosis. In addition to a positive reaction on the Monospot test, an infected person 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 Monospot 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 used to make the diagnosis.

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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 Monospot test. By requesting 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.

When the Monospot 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.

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Common Questions

1.  How serious is infectious mononucleosis?

The symptoms of the disease usually resolve without treatment in one to four months. Sometimes, your spleen or liver may enlarge, and you may have to limit your activity until these organs return to normal size. Heart problems or involvement of the central nervous system occur only rarely. Infectious mononucleosis may cause severe liver failure in males with a very rare special XLP gene. In this case, mononucleosis can be fatal.

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2.  Is mononucleosis really a "kissing disease"?

The spread of EBV requires intimate contact with saliva (found in the mouth) of an infected person. Kissing can transmit infection, but saliva on toys or hands can also transmit the virus. 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, and testing them for the virus is not practicable. For this reason, it is almost impossible to prevent the spreading of the virus.

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3.  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 Centers for Disease Control and Prevention’s website.

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4.  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.

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5.  Can EBV cause other serious illnesses?

EBV has been linked to certain cancers, such as Burkitt’s lymphoma, Hodgkin’s disease, nasopharyngeal carcinoma, and AIDS-related lymphoma, and continues to be studied for possible linkages to these and other cancers. All these diseases are rare.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.