title: Flow cytometry-based algorithm to analyze the anti-fixed Toxoplasma gondii tachyzoites IgM and IgG reactivity and diagnose human acute toxoplasmosis.
abstract: In the present study we evaluated the performance of a flow cytometry-based algorithm as a new serological approach to detect antibodies to T. gondii and specific IgG avidity to diagnose acute toxoplasmosis. The results showed that using FC-AFTA-IgM assay, all serum samples from patients with acute toxoplasmosis demonstrated seropositivity, whereas 90% of patients with chronic infection and 100% of non-infected individuals presented negative results. Thus, only 10% of patients with chronic toxoplasmosis showed residual IgM, in contrast with other methodologies used to diagnosis acute toxoplasmosis. On the order hand, FC-AFTA-IgG assay as well as FC-AFTA-IgG subclasses is unlikely to discriminate acute from chronic toxoplasmosis. We have also evaluated the performance of FC-AFTA-IgG avidity as a tool to exclude chronic toxoplasmosis in patients with positive FC-AFTA-IgM. Our data showed an excellent performance of FC-AFTA-IgG avidity employing the cut-off of 60% for Avidity Index (AI) with sensitivity and specificity of 100%. All serum samples from patients presenting acute toxoplasmosis showed low avidity index (AI≤60%), whereas all chronic patients showed high avidity index (AI>60%). The outstanding performance indexes of this novel flow cytometry-based algorithm support its use as a non-conventional alternative serological approach to diagnose human acute toxoplasmosis.
authors.affiliation: Núcleo de Doenças Infecciosas, Universidade Federal do Espírito Santo, Vitória, Espírito Santo, Brazil.
authors.forename: Priscila Pinto
authors.initials: PP
authors.lastname: Silva-dos-Santos
authors.forename: Geisa Baptista
authors.initials: GB
authors.lastname: Barros
authors.forename: José Roberto
authors.initials: JR
authors.lastname: Mineo
authors.forename: Deise Aparecida
authors.initials: DA
authors.lastname: de Oliveira Silva
authors.forename: Mauro Hygino Weinert
authors.initials: MH
authors.lastname: Menegaz
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Serufo
authors.forename: Reynaldo
authors.initials: R
authors.lastname: Dietze
authors.forename: Olindo de Assis
authors.initials: OA
authors.lastname: Martins-Filho
authors.forename: Elenice Moreira
authors.initials: EM
authors.lastname: Lemos
mesh_terms: D000465:Algorithms; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology*; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D007075:Immunoglobulin M / Q000097:blood / Q000276:immunology*; D012680:Sensitivity and Specificity; D014122:Toxoplasma / Q000276:immunology*; D014123:Toxoplasmosis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology* / Q000469:parasitology
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D007075:Immunoglobulin M