Tørring Tørring N N Aulesa Aulesa C C Eiben Eiben B B Ferri Ferri MJ MJ Nicolaides Nicolaides KH KH Ortiz Ortiz JU JU Performance characteristics of Elecsys free  β β hCG and PAPP-A for first trimester trisomy 21 risk assessment in gestational weeks 8+0 to 14+0 LaboratoriumsMedizin LaboratoriumsMedizin 2016 2016 40 40 21 21 9 9 10.1515/labmed-2015-0084 10.1515/labmed-2015-0084. Here, PAPPA is linked to trisomy 21.