Could PLATELIA Toxo IgM be the new gold standard for the serological diagnosis of congenital toxoplasmosis: a French multicenter study.

To assess the performance of PLATELIA Toxo IgM (Bio-Rad) and Toxo ISAGA (BioMérieux) to detect anti- Toxoplasma IgM in infants at risk of congenital toxoplasmosis, a retrospective multicenter study was conducted comparing serological results obtained in the framework of routine diagnosis work-up for congenital toxoplasmosis. All infants born to mothers infected with T. gondii during pregnancy from 2010 to 2020 with at least 6 months of serological follow-up were included ( n = 1,010). One thousand ten cases were included, of which 250 infants (24.75%) had congenital toxoplasmosis. A total of 1039 sera were included. The concordance between the two techniques was 96%, with kappa coefficient of 0.87, showing an almost perfect agreement between ISAGA and PLATELIA. Cumulative sensitivity and specificity were 73.2% and 99.5.% and 74.8% and 100% for ISAGA and PLATELIA, respectively. The mean time to detect IgM using ISAGA and PLATELIA tests was 6.9 ± 20.1 days and 5.6 ± 14.7 days, respectively not significant (ns). Finally, the sensitivity of ISAGA and PLATELIA to detect IgM antibodies in infected neonates at 5 days of life was 62% and 64%, respectively. Performances of PLATELIA Toxo IgM assay were comparable to the gold standard ISAGA. This enzyme-linked immunosorbent assay is suitable for routine serology for the diagnosis of congenital toxoplasmosis in newborns.IMPORTANCEThis study will help clinical microbiologists to chose an alternative serological method for the neonatal diagnosis of congenital toxoplasmosis, once the gold standard technique ISAGA will be withdrawn next year.