What is the difference between a non-invasive SANCO prenatal test and biochemical tests performed on mather’s blood?

Biochemical tests determine the level of biochemical markers such as pregnancy-associated plasma protein-A (PAPP-A) or the The β-subunit of hCG gonadotropin (beta-hCG) of the mother - not of the fetus. Their levels, together with the ultrasound result and other parameters (eg. age of the mother), are converted into the risk of trisomy with the use of a special software. The SANCO Test is about isolating the DNA of a child in the mother's blood (mainly from placental cells), and then analysing the DNA using new generation sequencing techniques and "measuring" its amount, which, in case of a trisomy, will exceed the assumed standard levels.