Elevated Toxoplasma IgG antibody in patients tested for infectious mononucleosis in an urban emergency department.

There are many infectious causes of fatigue, sore throat, and fever, including mononucleosis and toxoplasmosis. Toxoplasma antibody testing is rarely performed in most emergency departments; as a result, toxoplasmosis is diagnosed infrequently. We obtained Toxoplasma IgG IFA titers on ED patients who had mononucleosis testing performed to determine the frequency of toxoplasmosis in this population. Two hundred sixty patients were included in our study. Eleven (4.2%) had a positive mononucleosis test, and 14 (5.4%) had a positive Toxoplasma titer. In the detection of toxoplasmosis, Toxoplasma IgG titers of 1:1,024 or greater have been shown to be a sensitive means of detecting infection in the first six months. Further testing with IgM titers is needed to establish a positive diagnosis when necessary. We found more patients with elevated Toxoplasma IgG titers than with positive heterophil antibody titers in an ED population tested for mononucleosis over a two-year period. We conclude that toxoplasmosis may be as common as mononucleosis in our ED and that clinicians should consider this pathogen when working up patients with appropriate symptoms.