FIRST-TRIMESTER BIOCHEMICAL SCREENING FOR DOWN-SYNDROME WITH THE USE OF PAPP-A, AFP, AND BETA-HCG

Biochemical screening for Down syndrome (DS) is well established in th e second trimester of pregnancy, but there is little information avail able on its value in the first trimester. This study describes our pre liminary results with biochemical screening for DS in the first trimes ter of pregnancy in order to evaluate its efficacy at this time. Our s tudy population, including 19 DS pregnancies, was evaluated using mate rnal serum levels of a-fetoprotein (AFP), beta-human chorionic gonadot ropin (beta-hCG), and pregnancy-associated plasma protein A (PAPP-A). At a false positive rate (FPR) of 5 per cent, the detection rate (DR) for DS is 9 per cent for beta-hCG, 18 per cent for AFP, and 66 per cen t for PAPP-A when considering these parameters individually. With diff erent combinations of the analytes, the best detection rates are obtai ned with the association of PAPP-A and AFP (85 and 82 per cent DR for a 10 and 5 per cent FPR, respectively). Our data support the value of first-trimester biochemical screening for DS and that of PAPP-A as a s ingle marker.