Using “Degree of Extremeness” instead of “Multiples of Median” in first trimester risk assessment for Down syndrome—an improved method or just a gimmick in face of political motivations?

Introduction The concept of first trimester Down syndrome screening based on (NT) nuchal translucency measurement was introduced by the Fetal Medicine Foundation (FMF), London, in the late 1990s. For Germany, the mandate of NT training and auditing was assigned to the newly established German branch of the FMF in 2002. In January 2007, following the organisational split between FMF London and FMF Germany, the FMF Germany released its own, novel calculation software (“Prenatal risk calculation”, PRC), for this field. It is the aim of this study to compare the modified biochemical calculation method based on “Degree of Extremeness” (DoE) with the well-proven concept of “Multiple of Median” (MoM). Materials and methods The fβ-hCG and PAPP-A values of 266 first trimester examinations were categorised by gestational age, nicotine consumption and body weight. For each, a scatter plot and Pearson correlation was derived. As a second step, only patients with no nicotine consumption and a body weight between 55 and 65 kg were considered. The remaining 84 cases were again classified by gestational age and a statistical analysis was performed. Results The correlation of the DoEs with the respective MoM values was found to be quite good ( r = 0.76, P