SERUM PAPP-A AND FREE BETA-HCG ARE FIRST-TRIMESTER SCREENING MARKERS FOR DOWN-SYNDROME

Serum measurements of pregnancy-associated plasma protein A (PAPP-A) a nd the free P-human chorionic gonadotrophin (hCG) subunit were made in 13 women with Down syndrome (DS) pregnancies and six other women with fetal aneuploidy ascertained at chorionic villus sampling (CVS), as w ell as 89 women with contemporaneous normal control pregnancies. Media n serum PAPP-A measurements (0.31 MOM, 95 per cent confidence interval (CI) 0.22-0.65 vs. normal 1.06, 95 per cent CI 0.89-1.20)were lower a nd free beta-hCG subunit measurements.(1.13 MOM, 95 per cent CI 0.93-2 .63 vs, normal 0.91, 95 per cent CI 0.79-1.03) were higher at statisti cally significant levels. Receiver operator characteristic (ROC) curve s showed that the highest sensitivity for detection, 71.2 per cent (95 per cent CI 54.7-87.6 per cent), was for depressed PAPP-A levels; the combination of low serum PAPP-A levels, maternal age, and elevated fr ee beta-hCG levels yielded a detection rate of 78.9 per cent (95 per c ent CI 64.9-92.8 per cent) of the affected pregnancies at 8-12 weeks' gestation.