Prenatal diagnosis of congenital toxoplasmosis: A multicenter evaluation of different diagnostic parameters

OBJECTIVE: Our purpose was to evaluate different methods of diagnosing cong enital toxoplasmosis prenatally by amniocentesis and cordocentesis. STUDY DESIGN: In a retrospective multicenter study, we investigated consecu tive women who had seroconversion for Toxoplasma gondii during pregnancy an d who underwent either amniocentesis or cordocentesis or both to obtain a p renatal diagnosis of fetal toxoplasmosis. Data were obtained from 122 patie nts recruited in 6 different European Toxoplasma reference centers. infants born to these mothers were followed up until 1 year of age to confirm or e xclude congenital toxoplasmosis. Sensitivity, specificity, positive predict ive value, and negative predictive value were measured for the following pa rameters: (1) detection of the parasite in amniotic fluid by mouse inoculat ion, (2) detection of the parasite in amniotic fluid by in vitro cell cultu re, (3) detection of Toxoplasma deoxyribonucleic acid in amniotic fluid by a polymerase chain reaction assay, (4) detection of the parasite in fetal b lood by mouse inoculation, (5) detection of specific immunoglobulin M antib odies in fetal blood, and (6) detection of specific immunoglobulin A antibo dies in fetal blood. RESULTS: The polymerase chain reaction test performed on amniotic fluid had the highest level of sensitivity (81%) and also a high level of specificit y (96%). The combination of the polymerase chain reaction test and mouse in oculation of amniotic fluid increased sensitivity to 91%. The sensitivity o f immunoglobulins M and A in fetal blood was 47% and 38%, respectively. In congenitally infected fetuses a negative correlation was observed between p ositive serologic parameters and gestational age at the time of maternal in fection and at prenatal diagnosis. CONCLUSION: Congenital toxoplasmosis is best predicted by prenatal examinat ion with the combination of T gondii polymerase chain reaction and mouse in oculation of amniotic fluid. The role of cordocentesis in the diagnosis of congenital toxoplasmosis is limited.