INTERPRETATION OF HEMATOLOGIC AND SEROLOGIC FINDINGS IN THE DIAGNOSIS OF INFECTIOUS MONONUCLEOSIS

Abstract

Differential blood counts made at the time of the fever peak on 200 hospitalized patients showed a minimum of 20% atypical lymphocytes. In 370 patients neutrophil counts at the end of the febrile period never exceeded 49%. Precise statistical interpretation showed that, (1) We can state with 99.9% confidence that at least 96.6% of all future patients with mononucleosis will have atypical lymphocyte counts of 20% or higher. (2) We can state with 99.9% confidence that at least 98.2% of all future patients will have neutrophil counts of 49% or less. A case report of a patient with atypical pneumonia and a positive heterophil test illustrates a nonspecific anamnestic reaction of heterophil antibodies. This fact as well as the simple persistence of antibodies after a previous unrecognized attack of mononucleosis helps explain the paradox of a positive heterophil test unaccompanied by the typical clinical and hematologic findings of mononucleosis. While either a mononucleosis or a positive heterophil test gives assurance that the disease is infectious mononucleosis, each may occur independently in other situations. Not one or the other but both are essential to the diagnosis of mononucleosis.