Assessment of the IgA Immunosorbent Agglutination Assay for the Diagnosis of Congenital Toxoplasmosis on a Series of 145 Toxoplasmic Seroconversions

Abstract

A retrospective analysis of 145 medical records from our teaching hospital laboratory showed an overall specificity of greater than 97% for the IgA immunosorbent agglutination assay (ISAGA A) performed on the sera of babies to diagnose congenital toxoplasmosis (CT). These actualized data emphasize the ability of this test to confirm a diagnosis of congenital toxoplasmosis. Measuring IgA is considered useful for the postnatal detection of congenital toxoplasmosis (CT) (1, 2). IgA assessment was introduced into hyperspecialized tests used for the detection of congenital toxoplasmosis because it is more sensitive, and IgA is detectable for a longer period in newborns than is IgM (contrary to the situation in adult acute toxoplasmosis) and because of IgA's inability to permeate the placental barrier (2-5). To detect IgA, an IgA immunosorbent agglutination assay (ISAGA A) was shown to be more sensitive than enzyme-linked immunosorbent assay (ELISA) techniques (4, 6). However, focused evaluations of IgA and especially the ISAGA A remain scarce and were mainly published more than 15 years ago (4, 6-8). Moreover, more recent results from a European multicenter study were contradictory, showing close sensitivities of the ISAGA and ELISA and a relatively poorer specificity (Sp) of the ISAGA (91%) (9). In the current study, we retrospectively analyzed our daily routine records to determine if IgA assessment in babies is still of interest today and to provide an update on the performances of the commercial tests used in our laboratory.The medical records of 157 mothers who had experienced acute toxoplasmosis during or just before pregnancy were investigated. These patients were followed up from January 2006 to September 2012 in either the Grenoble teaching hospital or a peripheral center. All the samples were analyzed in the clinical laboratory of the Grenoble teaching hospital. For each newborn, the usual biological protocol was applied. Briefly, serum samples were taken 3 to 5 days after birth (the serum samples were not taken at birth to decrease the risk of detecting IgM transmitted by leakage) and, when possible, at 1 and 3 months of life to monitor the variations of antibody levels. Cord blood samples were also analyzed when available. To assess the levels of IgA, an ISAGA (Toxo ISAGA IgA; bioMérieux, Marcy l'Étoile, France) was prospectively performed according to the manufacturer's recommendations. Scores of Ն6 were considered positive, and scores of Ͻ3 were considered negative. The specificity and sensitivity (Ss) were calculated by comparing the ISAGA A results (positive or negative) with the final diagnoses, i.e., the presence or absence of congenital transmission, based on the complete radiological, clinical, and biological analyses of the cases. Biological interpretations were based upon the analyses of each sample with the following assays: Vidas Toxo IgG II and Toxo IgM (bioMérieux), IgG and IgM in-house immunofluorescence (10), comparative immunoblotting (Toxoplasma WB IgG IgM; LDBio, Lyon, France), and Toxo...

The global seroprevalence of anti-Toxoplasma gondii antibodies in women who had spontaneous abortion: A systematic review and meta-analysis

“…It is better to study IgA antibody in pregnant women to continue the evaluation of the acute form of T.gondii infection. IgA production is similar to that of IgM and it appears during the first week, whereas IgA antibody peak occurs later than IgM and persist more than 3 or 4 months following primary infection; therefore, they disappear earlier than IgM [127]. IgA may persist for more than a year [18,120,127].…”

“…IgA production is similar to that of IgM and it appears during the first week, whereas IgA antibody peak occurs later than IgM and persist more than 3 or 4 months following primary infection; therefore, they disappear earlier than IgM [127]. IgA may persist for more than a year [18,120,127]. Therefore, it is not also sufficient in the detection of acute infection in adults [128].…”

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“…La determinación de ambos marcadores fue importante ya que en dos niños sólo se pudo detectar IgA y en otro sólo IgM. Estos resultados coinciden con los obtenidos por otros autores 16,17 . La comparación entre la serología del neonato y la de su madre confirmó dos casos, en uno se detectó IgE positiva sólo en el suero del niño y en el otro los títulos de IgM, IgA e IgE fueron significativamente mayores en el suero del RN en dos muestras obtenidas con 10 días de diferencia 2 .…”