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

A.F Moron,A.M Amed,E Araujo Júnior,E.F.M Santana,F.M Andrade,J Bortoletti Filho,S.G.A Andrade

doi:10.12891/ceog4585.2019

Abstract

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.

Highlights

Even today, the diagnosis of fetal toxoplasmosis infection presents a serious challenge to obstetricians, because diagnosis implies invading the fetal environment to obtain fluid
The decision to perform amniocentesis is based on the analysis of maternal serology, which is not always simple to interpret due to the different methodologies used in clinical pathological examinations and serial repetition of serological tests in different laboratories when in doubt [1]
Diagnosis has evolved over time from amniocentesis and inoculation of the amniotic fluid in mice to cordocentesis, with non-specific and specific assessment of the fetal blood, and more recently to the use of the polymerase chain reaction (PCR) method applied to fetal fluids, especially amniotic fluid [2, 3]

Summary

Introduction

The diagnosis of fetal toxoplasmosis infection presents a serious challenge to obstetricians, because diagnosis implies invading the fetal environment to obtain fluid. Diagnosis has evolved over time from amniocentesis and inoculation of the amniotic fluid in mice to cordocentesis, with non-specific and specific assessment of the fetal blood, and more recently to the use of the polymerase chain reaction (PCR) method applied to fetal fluids, especially amniotic fluid [2, 3]. This evolution has led to the fulfilment of the true role of the specialist in maternal-fetal medicine: to assess the natural course of the disease through ultrasound, and to take action to preserve the fetus.

Methods

Results

Conclusion