Fetal DNA in maternal plasma as a screening variable for preeclampsia. A preliminary nonparametric analysis of detection rate in low-risk nonsymptomatic patients.

OBJECTIVE: Our objective was to examine whether plasma fetal DNA can be used as a screening variable in those women who developed preeclampsia but without any clinical symptom at the time of blood draw. METHODS: Fetal DNA was extracted from 1.5-mL plasma samples, and the DYS14 gene was analyzed by real-time quantitative polymerase chain reaction. Plasma collected and frozen from six women were each paired with five matched control samples of identical specimen type from gravid women carrying a presumed normal male fetus. Matched rank-sum analysis and nonparametric receiver operating characteristic (ROC) curves analysis of estimated multiples of median (MoM) were used for calculating detection rate (DR) and false-positive rate (FPR). RESULTS: The mean observed rank of 5.08 in the cases was significantly higher than the expected 3.18 (p-value = 0.013). Pregnancies that will develop a preeclampsia exhibit 2.39-fold higher levels of maternal plasma cell-free fetal DNA compared to matched controls. DR was 33 and 50% at an FPR of 5 and 10% respectively. CONCLUSIONS: The estimated DR allows to consider fetal DNA as a potential variable to predict preeclampsia in a low-risk population. Further studies will be addressed to calculate a parametric statistical algorithm and to estimate a proper posterior risk of the disease by means of fetal DNA alone or combined with other markers. Copyright 2004 John Wiley & Sons, Ltd.