The concept of a 3D firsttrimester screening cut-off

Objective: In classical firsttrimester screening according to Nicolaides a common age-depending backgroundrisk for trisomy 21 is modified by likelihood ratios to result in a so called 'adjusted risk'. At a cut-off of 1: 300 the resulting risk is considered as suspicious and an invasive testing should follow. Materials and methods: The measurement values can be visualized in a 3 dimensional scatter plot. The concept of a 3D risk assessment is based on the fact that chromosomal aberrations offer a typical constellation of elevated NT, lowered Papp-A and increased (trisomy 21) or decreased (trisomy 18, 13) fß-hCG.…