False positive infectious mononucleosis serology in epilepsy.

Positive serum tests for infectious mononucleosis (IM) unaccompanied by the clinical syndrome or blood changes characteristic of the disease were detected in 39/177 (22%) mentally subnormal patients investigated with three different commercially available IM slide tests. Slide positively was still detectable six months later in 27/35 (77%) positive reactors. Positive IM slide tests were significantly associated with anticonvulsant, primarily phenobarbitone therapy and with concomitant elevations of immunoglobulins IgG and IgM. Epstein Barr virus antibodies were not detectable in the sera of 8/38 (21%) positive slide reactors. The implications of these observations are discussed and attention is drawn to the variations in sensitivity, specificity, and comparability of different IM slide tests.