Infectious Mononucleosis(IM) test (Heterophilic antibodies- Monospot test)
Infectious Mononucleosis(IM) test (Heterophilic antibodies- Monospot test)
Infectious mononucleosis is a contagious disease frequently caused by a type of herpes virus called Epstein-Barr Virus (EBV). Referred to as kissing disease, it is commonly spread through saliva, while other less common modes of transmission include blood and semen during sexual contact, blood transfusions, and organ transplantations.
The mononucleosis (IM) test is among several laboratory tests used in diagnosing infectious mononucleosis. The test typically looks for two antibodies called heterophile antibodies that are made by the immune system in response to EBV infection. When these antibodies are exposed to horse red blood cells (used in the test), they clump the sample, indicating a positive reaction.
Heterophile antibodies are present in 90 to 95% of people at some point during the mononucleosis infection and remain detectable for up to a year.
What is the Mononucleosis Test Used For?
The Mononucleosis test is indicated for
Prompt diagnosis of patients who have symptoms suspected of infectious mononucleosis
Symptoms of Infectious Mononucleosis
Signs and symptoms of IM tend to overlap with the symptoms of other common viral illnesses and often include
Sore throat
Extreme tiredness
High fever
Tender lymph nodes along the back of the neck
Possible enlarged spleen and liver
Skin rash
Preparation for Test
Since the Monospot test requires a fingertip or vein blood sample, no specific preparation needs to be made before the test. However, it would be best to inform your doctor about any medications or supplements you take for accurate test results.
Interpretation of Test Results
The results of the Monospot test are given either positive or negative, with interpretations as follows:
Positive result(Abnormal)
The report indicates the presence of heterophile antibodies in patients with symptoms consistent with infectious mononucleosis. Yet, your doctor may still request an Epstein-Barr Virus(EBV) antibody test for a definitive diagnosis.
Negative results(Normal)
This report means no heterophile antibodies were detected at the time of testing. Most of the time, it means that you do not have infectious mononucleosis. Repeat testing, however, may be done to ensure the clearance of infection.
FAQs
When should I get tested with the Monospot Test?
If you have symptoms such as fever, headache, swollen glands, and tiredness, it's important to consult your doctor for the proper diagnosis. If they suspect you have infectious mononucleosis, they may recommend a heterophilic antibodies-Monospot test. Additionally, they will check for an enlarged spleen or liver during physical examination.
What does the positive result mean?
The clinical symptoms of mononucleosis, together with a positive result in the Monospot test, form the basis for IM diagnosis. In addition to this, an infected person may have more than the usual number of white blood cells(WBCs). Their heterophile antibodies decline after the fourth week of illness, and the Monospot test will become negative as the infection resolves.
Are there any risks associated with the Monospot Test?
When having a fingertip blood test or blood test from a vein, there is a slight possibility that you may have swelling, tenderness, slight pain, or excessive bleeding at the site of needle insertion and, on extremely rare occasions, infection. However, most symptoms go away quickly.
What factors influence the accuracy of Monospot test results?
The Monospot test is generally effective in detecting heterophile antibodies. However, under specific circumstances, it may produce relatively high rates of false-negative results, meaning the test shows you don't have mono when you actually do. These circumstances include performing the test early in the disease course, i.e., before one to two weeks of symptomatic onset or if you are an infant or child under the age of 4.
In rare cases, the test may give a false-positive result even when the person may not have mononucleosis. And this may occur in people with:
- Hepatitis
- HIV infection
- Cancer
- Rubella
- Systemic lupus erythematosus
- Toxoplasmosis
What are heterophile antibodies?
Originally described by Paul and Bunnell, heterophile antibodies are a type of immunoglobulin M (IgM) antibodies that cause clumping of red blood cells (RBCs) from various animals like cows, sheep, horses, and goats. They are also directed against the specific antigens on RBCs frequently detected in the sera of patients with IM.
Heterophile antibodies usually are present in 90% to 95% of people with mononucleosis infection. However, they cannot be detected in infants and children under the age of 4 years.
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