False positive mono test cause? qualitative labcorp negative, ebv latent ab strongly positive but no acute or reactivated infection. high wbc, neutrophils, low lymphocytes. cefixime seemed to be working, bacterial culture grew nothing. ideas?

You have not provided any data to suggest what the original problem was. Without that data, the material posted does not provide enough for a reasoned response. You are welcome to start over. Posts are not linked so each needs the relevant data and question.

Monospot test is useful as a screening test when infectious mononucleosis, so called "mono" is suspected, however, positive test should be confirmed by serologic testing of EBV-specific antibody response. You did not have a typical mono. False positive monospot (heterophil antibody) is less than 10%, usually resulting from erroneous interpretation.