Human parvovirus B19: Hard to differentiate from infectious mononucleosis

EDITOR, - J R Pattison's editorial prompts us to report recent difficulties that we encountered in differentiating between infectious mononucleosis and parvovirus B19 infection.1 Fever, pharyngitis, lymphadenitis, and abnormal mononuclear cells in the peripheral blood are the characteristic features of infectious mononucleosis. In most laboratories t e diagnosis is now made or reinforced by the finding of heterophil antibodies on latex agglutination testing. Such testing is based on the agglutination of latex particles coated with the highly purified Paul-Bunnell antigen derived from red cell membranes.2 False positive results have rarely been reported, and the test is regarded as highly specific. Confirmation is normally unnecessary,3 but the manufacturers of the kit that we use (Monolatex, Biokit, Kent) state that the results of the assay should be …