Proteomics and Down syndrome screening: a validation study

Abstract

In a previous discovery study, we identified seven potential screening markers for Down syndrome (DS). Here, we report on an extended study to validate the discriminative potential of these markers. Concentrations of the seven analytes were measured using bead-based multiplexed immunoassays in maternal serum from 27 DS pregnancies and 27 matched controls. Control samples were matched to the cases by gestational age (exact day), maternal weight ( ± 5 kg), and maternal age ( ± 1 year) and by closest sample date. Prediction values were obtained for current screening markers [pregnancy-associated plasma protein A (PAPP-A), free beta human chorionic gonadotrophin (fβ-hCG) and nuchal translucency (NT)] and seven markers identified before based on concentration fold ratios between DS and controls. Models were fitted based on data of the discovery study or this study and also tested on both datasets. A significantly higher fold ratio was only found for epidermal growth factor (EGF) (-1.96; p = 0.006). In the prediction model for the current dataset, EGF improved the detection rate (DR) of DS by 5.7% [at a fixed 5% false-positive rate (FPR)] when added to the currently used screening markers. Validation of previously identified biomarkers only confirmed EGF for further consideration as a DS screening marker. This underlines the importance of validating biomarkers; in this study, limiting the range of plausible biomarkers to only one suitable biomarker.