Monospot test

The monospot test, also known as the heterophile antibody test, 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. [Elgh F, Linderholm M, Clinical and Diagnostic Virology 7 (1996) 17-21 http://dx.doi.org/10.1016/S0928-0197(96)00245-0] This means that if you do not have the infection, it is unlikely (0-4% chance, depending on whose estimate you believe - the real chance is just one number for a given test) that the test will be wrong. If you do have the infection, the sensitivity tells us that there is an 8% to 30% that the test will nevertheless report that you do not have the infection. A monospot test will identify a current infection. 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 some cells in the body for the rest of the carrier's life.

Diagnosis, must have atypical lymphocytes in peripheral blood smear and this characteristic heterophile antibody, that convalence, agglutinates red blood cells of other specifies (esp. sheep and horse).

The Monospot test relies on the agglutination of horse RBCs by heterophile antibodies in patient's serum. This explains what is meant by heterophile antibody, in that it reacts with proteins across species lines. [ [http://dictionary.reference.com/search?q=heterophile heterophile - Definitions from Dictionary.com ] ]

It is indicated in fever, malaise, pharyngitis, tender lymphadenitis (especially posterior cervical; often called "tender glands") and splenomegaly (enlarged spleen).Davidson's Principles & Practices of Medicine 20th ed ] 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.

In this case an immunofluorescence is useful for acute infection, with the following characteristics:- VCAs (antiviral capsid antibodies) 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.

References