Clinical and Interpretive

This assay is used for rapid confirmation of a diagnosis of infectious mononucleosis.

Infectious mononucleosis (IM) is a viral illness that involves reticuloendothelial tissue and is generally limited to children and young adults. IM is most commonly caused by Epstein-Barr virus (EBV). The disease is characterized by fever, sore throat, lymphadenopathy, headache, and fatigue, and on a symptomatic basis may be confused with other diseases. Detectable levels of the infectious mononucleosis (IM) heterophile antibody can usually be expected to occur between the sixth and tenth day following the onset of symptoms. The level usually increases through the second or third week of illness and, thereafter, can be expected to persist, gradually declining over a 12-month period.

Approximately 10% of patients with infectious mononucleosis (IM) will have no heterophile antibody and may require Epstein-Barr virus (EBV) antibody tests to confirm the diagnosis.

False-negative results have been reported. Some of these may represent cases of IM that remain persistently seronegative for the IM heterophile antibody. However, some false-negative results have been shown to be due to a delayed IM heterophile antibody response.

IM heterophile antibody titers have been shown to persist in some cases for months and years after clinical symptoms have subsided. Conversely, IM heterophile antibodies have been detected prior to the onset of clinical symptoms. Thus, caution should be exercised in the interpretation of test results.

The IM heterophile antibody has been associated with several diseases other than IM. These include leukemia, Burkitt’s lymphoma, pancreatic carcinoma, viral hepatitis, cytomegalovirus infections, and others. In these cases, it is difficult to disprove the possibility of concurrent disease states.

Some segments of the population do not produce detectable heterophile antibodies, eg, approximately 50% of children <4 years of age and 10% of adolescents.