title: Comparison of two commercially available avidity tests for toxoplasma-specific IgG antibodies.
abstract: BACKGROUND
  IgG anti-Toxoplasma avidity tests have proven useful to discriminate between recent and distant infection in management of pregnant women with anti-Toxoplasma-IgM antibodies. This study was performed to compare two commercially available IgG anti-Toxoplasma avidity test kits.
  
  
  METHODS
  Sixty-four samples positive for IgM and IgG anti-Toxoplasma antibodies were analyzed with two IgG anti-Toxoplasma avidity tests: VIDAS Toxo IgG avidity kit (BioMérieux, Marcy-l'Etoile, France) and Toxoplasma gondii IgG avidity EIA kit (Labsystems, Helsinki, Finland). Samples were obtained from both pregnant women and subjects in different clinical settings.
  
  
  RESULTS
  Of 64 sera positive in both VIDAS Toxo IgG and VIDAS Toxo IgM tests, 19 (29.7%) had high avidity antibodies in VIDAS and 17 (26.6%), high avidity antibodies in Labsystems kit. A total of 48 (75.0%) of 64 sera showed concordant results between VIDAS and Labsystems Toxo IgG avidity tests; one (1.2%) serum sample showed discordant results and in 15 (23.4%) sera, results were high or low in one test and borderline in the other. Overall correlation coefficient for results obtained in both tests was 0.80 (0.60 in sera of pregnant women and 0.88 in sera of other patients, respectively).
  
  
  CONCLUSIONS
  Correlation between results obtained in BioMérieux and Labsystems Toxo IgG avidity kits in sera from pregnant women as well other individuals was high. BioMérieux assay possesses the advantage of automatization but requires the VIDAS machine; in contrast, Labsystems assay is less costly but requires time-intensive manual performance and calculation of test results.
authors.affiliation: Department of Medical Microbiology and Immunology of Infection, Institute for Infection Medicine, Benjamin Franklin Medical Center, Free University of Berlin, Germany.
authors.forename: Cosme
authors.initials: C
authors.lastname: Alvarado-Esquivel
authors.forename: Shneh
authors.initials: S
authors.lastname: Sethi
authors.forename: Klaus
authors.initials: K
authors.lastname: Janitschke
authors.forename: Helmut
authors.initials: H
authors.lastname: Hahn
authors.forename: Oliver
authors.initials: O
authors.lastname: Liesenfeld
mesh_terms: D000818:Animals; D000915:Antibody Affinity; D002624:Chemistry, Clinical / Q000379:methods; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods; D007074:Immunoglobulin G / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D011247:Pregnancy; D015203:Reproducibility of Results; D014122:Toxoplasma / Q000276:immunology*; D014123:Toxoplasmosis / Q000175:diagnosis
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M