Total cell-free DNA (beta-globin gene) distribution in maternal plasma at the second trimester: a new prospective for preeclampsia screening.

OBJECTIVES: Levels of cell-free foetal DNA (f-DNA) in maternal plasma are higher in those asymptomatic subjects who will eventually develop preeclampsia. f-DNA is, however, informative only for those women bearing a male foetus, by amplification of Y-specific sequences and represents a small fraction of total circulating DNA that can be dosed by using ubiquitous genes as well as beta-globin. In this study, we examined the quantitative distribution of total DNA by amplification of beta-globin gene, in asymptomatic women matched with controls to evaluate its possible role in predicting preeclampsia. METHODS: Forty-eight low-risk women (8 asymptomatic cases matched for gestational age at the second trimester with 40 controls) were enrolled in the present study. beta-globin concentrations were converted into multiples of the median of the controls (MoM), in order to assess the possible different distribution of beta-globin MoM in cases and controls. RESULTS: MoM values were as follows: controls, 1.00 +/- 0.59; asymptomatic cases, 1.99 +/- 1.95. After Gaussian conversion of data, at a false-positive rate (FPR) of 5%, the detection rate (DR) was 46%. CONCLUSION: beta-globin (total DNA) levels are higher in those patients who subsequently developed preeclampsia and can potentially be used in screening for early detection of the disease. These findings represent a step forward in the study of cell-free DNA in maternal blood as a screening variable, because it overcomes the gender limitations of foetal DNA screening. Copyright (c) 2004 John Wiley & Sons, Ltd.