title: Evaluation of a new protocol for retrospective diagnosis of congenital toxoplasmosis by use of Guthrie cards.
abstract: The aim of this study was to assess the diagnostic value of IgM Western blotting (WB), IgA enzyme immunoassay (EIA), and DNA amplification by real-time PCR on Guthrie cards to retrospectively establish the diagnosis of congenital toxoplasmosis (CT). To this purpose, Guthrie cards were collected from 18 infants born to mothers with primary Toxoplasma gondii infection during pregnancy. Moreover, the analytical sensitivity of T. gondii PCR was assessed by testing mock dried blood specimens set up with several known DNA dilutions. IgM WB was demonstrated to be the most sensitive method. When the results of T. gondii DNA detection and specific IgM recovery were combined, retrospective CT diagnosis by using Guthrie cards was established in 3 out of 6 infected infants (sensitivity, 50%; 95% confidence interval, 26.8% to 73.2%). No positive PCR or serologic results were found in the group of 12 uninfected infants, demonstrating the excellent specificity of the three methods (95% confidence interval, 78.1% to 99.5%). The findings of the present study suggest that, in cases of missed diagnosis of CT at birth, analysis of Guthrie cards for children with compatible clinical findings after the perinatal period, in particular the combination of recovery of specific IgM antibodies and T. gondii DNA amplification, could be helpful. Nevertheless, since suboptimal conditions of storage of dried blood specimens can seriously affect sensitivity, negative results cannot rule out CT diagnosis. In contrast, because of the excellent specificity shown by IgM serologic testing and T. gondii DNA amplification on Guthrie cards, positive results obtained by either of the two methods should be considered diagnostic.
authors.affiliation: Microbiology, DIMES, University of Bologna, Bologna, Italy antonella.marangoni@unibo.it.
authors.forename: Antonella
authors.initials: A
authors.lastname: Marangoni
authors.affiliation: Department of Obstetrical, Gynaecological and Paediatric Sciences, Operative Unit of Neonatology, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Capretti
authors.affiliation: Department of Obstetrical, Gynaecological and Paediatric Sciences, Operative Unit of Neonatology, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Morena
authors.initials: M
authors.lastname: De Angelis
authors.affiliation: Microbiology, DIMES, University of Bologna, Bologna, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Nardini
authors.affiliation: Microbiology, DIMES, University of Bologna, Bologna, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Compri
authors.affiliation: Microbiology, DIMES, University of Bologna, Bologna, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Foschi
authors.affiliation: Department of Obstetrical, Gynaecological and Paediatric Sciences, Operative Unit of Neonatology, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Azzurra
authors.initials: A
authors.lastname: Orlandi
authors.affiliation: Department of Obstetrical, Gynaecological and Paediatric Sciences, Operative Unit of Neonatology, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Concetta
authors.initials: C
authors.lastname: Marsico
authors.affiliation: Department of Hematology, Oncology and Laboratory Medicine, Centralized Laboratory of St. Orsola-Malpighi Hospital, Bologna, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Righetti
authors.affiliation: Department of Obstetrical, Gynaecological and Paediatric Sciences, Operative Unit of Neonatology, St. Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Faldella
authors.affiliation: Microbiology, DIMES, University of Bologna, Bologna, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Cevenini
mesh_terms: D000913:Antibodies, Protozoan / Q000032:analysis; D015153:Blotting, Western; D016054:DNA, Protozoan / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D012680:Sensitivity and Specificity; D012698:Serologic Tests; D014122:Toxoplasma / Q000302:isolation & purification*; D014125:Toxoplasmosis, Congenital / Q000175:diagnosis* / Q000469:parasitology
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan