Screening for toxoplasmosis during pregnancy: One-year experience in an Italian reference laboratory

Abstract

AIMS: To describe the experience of the Toxoplasmosis Laboratory of Infectious Disease Department University of Pavia, IRCCS Foundation, San Matteo Polyclinic Pavia, a reference laboratory for diagnosis of toxoplasmosis, in the investigation of pregnant women with suspected acute toxoplasmosis. METHODS: All sera were tested with LIAISON® Toxo IgM and IgG II, Toxo IgG Avidity II kits (DiaSorin, Saluggia, Italy), VIDAS Toxo IgG II and Toxo IgG Avidity (bioMérieux, Marcy l’Etoile, France ), IgM ISAGA (bioMérieux, Marcy l’Etoile, France) and ETI-TOXOK-A reverse PLUS (DiaSorin, Saluggia, Italy). When required (IgG negative/IgM positive women), IgG/IgM Western Blot II (LDBio, Lyon, France) was also performed. Prenatal diagnosis on amniotic fluid was done by nested PCR. All newborns were followed up to one year of age in order to exclude or confirm the diagnosis of congenital toxoplasmosis. All pregnant women with acute or undetermined stages of infection were treated. RESULTS: In the course of 2007, 236 women with suspected acute (IgM-positive) Toxoplasma infection were followed up. In the reference laboratory, 91 women had test results indicating acute toxoplasmosis, and 10 had undetermined status of infection. These 101 patients represented 42.8% of the 236 women referred. Acute toxoplasmosis could be excluded in the remaining 135 patients, of whom 53 were non-immune. Three infected newborns were observed, all from mothers tested for the first time during the third trimester of pregnancy. CONCLUSIONS: The role of a reference laboratory in suspected toxoplasmosis acquired during pregnancy is crucial to date the infection and discriminate between seroconversion and false positive anti-Toxoplasma IgM antibodies. This avoids unnecessary anxiety in immune women, provides correct counseling about primary prevention and periodic testing for seronegative ones, and allows early treatment and follow-up of pregnant women with acute infection and their newborns.