Use of Enzygnost Anti-human IgA conjugate in combination with the kit Enzygnost toxoplasmosis IgG (Siemens Healthcare Diagnostics) for the detection of IgA anti-Toxoplasma gondii

Laboratory diagnosis of toxoplasmosis is mainly based on serological methods, particularly important in the most challenging situations, as the diagnosis of primary infection during pregnancy and diagnosis of congenital infection. Tests for the detection of IgA antibodies are especially important in the newborns, because they are more sensitive than IgM conventional methods. The purpose of this study was to evaluate diagnostic performances of Enzygnost system for IgA detection, achieved by using Enzygnost Anti-human IgA/POD conjugate in combination with Enzygnost toxoplasmosis IgG (Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany). A retrospective study was performed with 591 serum samples submitted to the Microbiology Laboratory of S. Orsola Hospital in Bologna for toxoplasmosis screening.All the sera were tested by Enzygnost toxoplasmosis IgG, Enzygnost toxoplasmosis IgM and Enzygnost system for IgA (Siemens Healthcare Diagnostics). Border-Line or positive IgM results were confirmed by Vidas Toxo IgM (bioMerieux, Marcy l’Etoile, France). Finally, IgG Avidity was performed by Vidas Toxo IgG Avidity (bioMerieux) and LDBio Toxoplasma WB IgG/IgM (LDBio Diagnostics, Lyon, France). During the study period, 453 sera were IgA negative, 53 were Border-Line and 85 were positive when tested by Enzygnost system for IgA. No significative correlation was found between IgA positive results and low Avidity results.Three babies were correctly diagnosed as congenital toxoplasmosis infected infants because of the presence of IgA antibodies at birth. Enzygnost system for IgA anti-Toxoplasma showed good diagnostic performances.We conclude that the high sensitivity and specificity of and its suitability for automation make it an ideal screening test.