Department of Haematology


The heterophile antibody response to Epstein-Barr Virus (EBV) that gives a positive result is usually detectable between the 5th and 10th day of illness, reaching a peak in the second to third week and persisting for several months.

In the presence of abnormal results or atypical cell flagging by the Full Blood Count analyser, a blood film is also examined. The presence of atypical mononuclear cells on the film is not specific for Infectious Mononucleosis. Where the film shows atypical mononuclear cells and the slide test is negative, the laboratory will suggest a repeat FBC and slide test in 7-10 days.

Infectious mononucleosis due to infectious agents other than EBV does not produce a heterophile antibody. It is also known that sometimes patients (particularly children) do not produce a heterophile antibody to EBV either, specifically this is up to 20% of adults and up to 50% of young children. If this occurs a positive diagnosis may be made by sending a sample to Microbiology for EBV serology.

Test performed at GRH.

Sample Requirements

4ml EDTA or, preferrably, a clotted serum sample (5ml Gold-top SST tube or 3.5ml Rust-top gel tube)

EDTA with cap


Gold top with cap
  • The same EDTA sample may be used for FBC and the slide test.
  • The EDTA sample is only valid for 24 hours for the IM test
  • A clotted sample is valid for 7 days for the IM test

Turnaround Time

Next working day

Reference Ranges

N/A. The IM slide test will be reported as positive or negative.

Time limit for add ons

Up to 24 hours for an EDTA sample and 7 days for a clotted sample from the time of venepuncture, when refrigerated.

Interfering Substances

False positive reactions have been reported in serum samples from patients with recent CMV, Hepatitis A, parvovirus and leptospira infection.

Haemolysed or contaminated samples are not suitable for analysis.