Persistent falsely positive rapid tests for infectious mononucleosis. Report of five cases with four--six-year follow-up data.

In many laboratories, rapid slide tests incorporating differential absorption have replaced heterophil antibody tube tests in the investigation of suspect infectious mononucleosis. The present report describes serologic data from five individuals whose Monospot tests remained falsely positive for four years or more without other evidence of infectious mononucleosis or underlying disease states. Three of the five had never been infected with the Epstein-Barr virus. All five had negative results when studied with the ox cell hemolysin and the horse cell differential absorption tube tests. False-positive test results have also been encountered in healthy controls, as frequently as in patients with underlying disease states. The authors are unable to attach any clinical significance to the findings of an isolated falsely positive Monospot test even when it persists for many months or years.