Second-trimester maternal serum screening for Down's syndrome: free beta-human chorionic gonadotrophin (HCG) and alpha-fetoprotein, with or without unconjugated oestriol, compared with total HCG, alpha-fetoprotein and unconjugated oestriol.
The aim of our study was to compare three protocols for second-trimester maternal serum screening for Down's syndrome in the same serum samples, using two triple tests [total human chorionic gonadotrophin (HCG), alpha-fetoprotein, unconjugated oestriol; and free beta-HCG, alpha-fetoprotein, unconjugated oestriol] and a double test (free beta-HCG and alpha-fetoprotein). The three protocols were compared in a series of 23 serum samples from Down's syndrome pregnancies and in a cohort of 2516 pregnant women receiving routine antenatal care between June 1992 and June 1993. Among the 23 affected cases, at a cut-off risk of 1:380, the detection rate of Down's syndrome was comparable with the double test (74%; 17/23) and the triple tests (65%; 15/23) (not significantly different). At the same cut-off risk, in the cohort of 2516 pregnant women screened between 15 and 18 weeks gestation, both protocols using free beta-HCG achieved a significant reduction of the number of false positive cases (P = 0.013 and 0.004 for double and triple tests respectively). We conclude that, compared to total HCG, alpha-fetoprotein and unconjugated oestriol, use of free beta-HCG and alpha-fetoprotein represents a better second-trimester screening test for Down's syndrome, because it significantly decreases the false positive rate at a lower running cost. The addition of unconjugated oestriol to the double test adds no further advantage.
Extermann
P
P
Department of Obstetrics and Gynaecology, Geneva University Hospital, Switzerland.
Bischof
P
P
Marguerat
P
P
Mermillod
B
B
D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood*; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis*; D004964:Estriol / Q000097:blood*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D011237:Predictive Value of Tests; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D018566:Pregnancy, High-Risk; D011296:Prenatal Diagnosis / Q000379:methods*; D011446:Prospective Studies; D000509:alpha-Fetoproteins / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D004964:Estriol