The role of serology in active ocular toxoplasmosis

Our purpose was to examine toxoplasmic serology in relation to episodes of suspected acute toxoplasmic retinochoroiditis and evaluate its use in the appraisal of patients. The mean values of enzymatic immunoassay (EIA) titers for toxoplasmic antibodies were retrospectively compared in patients with active and inactive toxoplasmosis and in a third group of uveitis cases not caused by toxoplasmosis. The proportion of cases under and above a predefined serology value above cut-off was compared in all groups. Between 1995 and 2010, 97 out of 1,276 new uveitis cases seen at the Centre for Ophthalmic Specialized Care (COS), Lausanne, Switzerland were diagnosed as toxoplasmic retinochoroiditis, of which 51 had documented serology available. The mean EIA values for immunoglobulin (Ig) G were 147.75 ± 259.4 IU/ml for patients with active disease, 18.93 ± 23.09 (p < 0.05) for patients with inactive toxoplasmosis and 18.35 ± 20.82 for controls (p < 0.017). The proportion of cases under the designated limit value were 2/51 (4%) in the active retinitinochoroiditis group, 14/27 (52%) (p < 0.05) in the control group, and 7/7 (100%) in the inactive toxoplasmic group (p < 0.001). Three out of 51 cases showed high IgM values in addition to IgG elevation and were primary infections. Toxoplasmosis serology, contrary to popular belief, is useful to confirm active toxoplasmic retinochoroiditis; it is easy to perform, cheap and supports clinical diagnosis in up to 96% of cases, not only by showing positivity but by also showing a significant elevation of titers. In atypical cases serology is not only useful but essential.