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Monospot test: Wikis


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The monospot test, a form of the heterophil antibody test,[1] is a rapid test for infectious mononucleosis due to Epstein-Barr virus (EBV). The test is sensitive for heterophile antibodies produced by the human immune system in response to EBV infection. Commercially-available test kits are 70-92% sensitive and 96-100% specific.[2] It will generally not be positive during the 4-6 week incubation period before the onset of symptoms. It will also not generally be positive after active infection has subsided, even though the virus persists in the same cells in the body for the rest of the carrier's life.


The Monospot test relies on the agglutination of horse RBCs by heterophil antibodies in patient's serum. This explains what is meant by heterophil antibody, in that it reacts with proteins across species lines. [3] A 20% suspension of horse red cells is used in an isotonic 3-8 % sodium citrate formulation. One drop of the patient’s neat serum to be tested is mixed on an opal glass slide with one drop of a particulate suspension of guinea-pig kidney stroma, and a suspension of beef red cell stroma; sera and suspensions are mixed with a wooden applicator for 10 times. Ten micro liter of the horse red cell suspension are then added and mixed with each drop of absorbed serum. The mixture is left undisturbed for one minute (not rocked or shaken). Examine for the presence or absence of red cell agglutination. If stronger with the sera absorbed with guinea-pig kidney, the test is positive. If stronger with the sera absorbed with beef red cell stroma, the test is negative. If agglutination is absent in both mixtures, the test is negative. A known 'positive' and 'negative' control serum is tested with each batch of test sera.


It is indicated in fever, malaise, pharyngitis, tender lymphadenitis (especially posterior cervical; often called "tender glands") and splenomegaly (enlarged spleen).[4]

Differential diagnosis for pharyngitis is extensive, and includes Streptococcal infection and other Upper Respiratory Tract Infections.

However, children particularly, as well as a tenth of infected adolescents with Infectious Mononucleosis do not produce the heterophile antibody at any stage. Others might have a negative test (due to delayed seroconversion) and thus, the test should be repeated. [4]

In this case an immunofluorescence is useful for acute infection, with the following characteristics:, VCAs (Viral Capsule Antigen) in the IgM class, antibodies to EBV early antigen, absent antibodies to EBV nuclear antigen (anti-EBNA)

It is more useful to know the positive predictive value (chance of a positive test being associated with disease), but this depends on the population tested, not just the test.


  1. ^ Basson V, Sharp AA (May 1969). "Monospot: a differential slide test for infectious mononucleosis". J. Clin. Pathol. 22 (3): 324–5. PMID 5814738. PMC 474075.  
  2. ^ Elgh F, Linderholm M, Clinical and Diagnostic Virology 7 (1996) 17-21
  3. ^ heterophil - Definitions from
  4. ^ a b Davidson's Principles & Practices of Medicine 20th ed


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