Monospot test

Monospot test
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Purpose	Diagnosis of infectious mononucleosis
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The Monospot test is a serological test used to detect heterophile antibodies in the blood, which are typically present during an infection with Epstein-Barr virus (EBV), the causative agent of infectious mononucleosis. This test is commonly used in clinical settings to aid in the diagnosis of infectious mononucleosis, especially in adolescents and young adults.

Principle

The Monospot test is based on the principle of agglutination. When a patient's serum containing heterophile antibodies is mixed with horse or sheep red blood cells, these antibodies cause the red blood cells to clump together, or agglutinate. This agglutination is visible to the naked eye and indicates a positive test result.

Procedure

The procedure for the Monospot test involves several steps:

1. A blood sample is collected from the patient.
2. The serum is separated from the blood cells by centrifugation.
3. The serum is then mixed with a suspension of horse or sheep red blood cells.
4. The mixture is observed for agglutination, which typically occurs within a few minutes.

Interpretation

A positive Monospot test indicates the presence of heterophile antibodies, which are commonly associated with infectious mononucleosis. However, it is important to note that the test is not specific for EBV and can occasionally yield false-positive results due to other conditions such as systemic lupus erythematosus, rheumatoid arthritis, or other viral infections.

A negative Monospot test does not completely rule out infectious mononucleosis, especially in the early stages of the disease or in young children, who may not produce heterophile antibodies. In such cases, additional testing, such as specific EBV serology, may be required.

Clinical Use

The Monospot test is most useful in the following scenarios:

• Adolescents and young adults presenting with symptoms of infectious mononucleosis, such as fever, sore throat, and lymphadenopathy.
• When a rapid diagnosis is needed to differentiate infectious mononucleosis from other causes of similar symptoms, such as streptococcal pharyngitis.

Limitations

The Monospot test has several limitations:

• It may not detect heterophile antibodies in young children, leading to false-negative results.
• False-positive results can occur due to other conditions that produce heterophile antibodies.
• It does not provide information about the stage of EBV infection or differentiate between acute and past infections.

Alternatives

When the Monospot test is negative or inconclusive, other tests may be used to diagnose infectious mononucleosis:

• EBV serology: Tests for specific antibodies to EBV antigens, such as VCA-IgM, VCA-IgG, and EBNA antibodies.
• Complete blood count (CBC): May show atypical lymphocytes and elevated white blood cell count.

History

The Monospot test was developed in the 1930s and has since become a standard diagnostic tool for infectious mononucleosis. It was one of the first tests to utilize the principle of heterophile antibody detection, paving the way for other serological tests.

See also

• Infectious mononucleosis
• Epstein-Barr virus
• Heterophile antibodies