Polymerase chain reaction analysis of amniotic fluid for diagnosis of fetal toxoplasmosis

Abstract

Polymerase chain reaction analysis of amniotic fluid for diagnosis of fetal toxoplasmosis F.M. Andrade1, E.F.M. Santana1, E. Araujo Júnior1, S.G.A. Andrade1, J. Bortoletti Filho1, A.M. Amed1, A.F. Moron1 1Department of Obstetrics, Paulista School of Medicine, São Paulo Federal University (EPM-UNIFESP), São Paulo (Brazil) Summary Purpose: To assess the efficacy of the polymerase chain reaction (PCR) analysis of the amniotic fluid to diagnose fetal toxoplasmosis. Material and Methods: The PCR method was used to test amniotic fluid via the B1 primer for detecting T. gondii in pregnant women whose serology was positive for IgM. To validate the method, 84 pregnant women underwent amniocentesis and were followed-up for a period of six years. All the newborns were assessed using serology (IgM), transfontanellar ultrasound, and examination of the fundus. Results: The positive PCR rate for the etiologic agent of toxoplasmosis was 17.9% (15 patients) and the rate of newborns in contact with this agent was 16.7% (14 infants). Of these 14 infants, five manifested the disease, while nine only had contact with T. gondii with no signs of toxoplasmosis until hospital discharge. Of the five newborns with the disease, three were born to women who had a negative pre-natal PCR. The PCR method had a sensitivity of 78.6%, specificity of 94.3%, positive predictive value of 73.3%, and negative predictive value of 95.6%. Conclusion: The PCR method is effective in detecting congenital toxoplasmosis and leads us to question the efficacy of maternal serological status as a diagnostic marker. Key words: Polymerase chain reaction; Amniotic fluid; Toxoplasmosis.