Toxoplasmic lymphadenitis--clinical and serologic profile.

Objective: To study the serologic profile of several types of test for toxoplasmosis, in order to contribute to the interpretation of antibody kinetics.

Methods: The clinical and serologic features of 120 cases of lymphadenopathy with known time of clinical onset were studied during 18 months postinfection. Antibody kinetics was determined by Sabin-Feldman dye test, complement fixation with light antigen, IgM immunofluorescent antibody test, and IgM immunosorbent agglutination assay (IgM-ISAGA). Cell-mediated immunity was evaluated by the toxoplasmin skin test.

Results: Seventy-five female patients aged 11-54 years (median 27 years) and 45 male patients aged 3-59 years (median 17 years) were studied, 85% of whom were under 30 years of age. Cervical lymph nodes were involved throughout, generally on both sides, with more than one affected ganglion group in 88%. The predominant symptom was asthenia (69%), which persisted in some cases for several months. A negative Sabin-Feldman dye test in a lymphadenopathy with more than three weeks' evolution excludes a toxoplasma etiology. A positive Sabin-Feldman dye test with negative IgM-ISAGA almost invariably excludes recent infection. The Sabin-Feldman dye test was positive in 94% of patients with titers higher than 1 : 16 000 within the first three months. The IgM-ISAGA yielded 98% of positive results, of which 94% were high titers. Titers >/= 1 : 160 in the IgM immunofluorescent antibody test and complement fixation were found to be highly indicative of recent infection, since 87% and 91%, respectively, were found within the first three months. A negative skin test plus positive serology values indicates recent infection.

Conclusion: Our results indicate that estimation of time of infection on the basis of serologic results is improved by the simultaneous application of several tests, and correlates closely with the presence of clinical lymphadenitis.