OBJECTIVE: Our purpose was to compare the efficacy of triple-marker screening 
(alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin) with 
alpha-fetoprotein plus free beta-human chorionic gonadotropin.
STUDY DESIGN: Free beta-human chorionic gonadotropin was concurrently assayed in 
2349 maternal serum samples. Trivariate and bivariate algorithms were used to 
calculate the risk for fetal Down syndrome by the two protocols. Free beta-human 
chorionic gonadotropin from 12 cases of fetal Down syndrome previously screened 
with the triple marker was retrospectively assayed.
RESULTS: Mean maternal age of our study was 29.8 years (range 14 to 51 years). 
The initial screen-positive rate with the triple marker was 8.0% compared with 
12.8% for alpha-fetoprotein plus free beta-human chorionic gonadotropin. All 
three cases of fetal Down syndrome ascertained in our prospective study were 
detected by the triple marker; in contrast, one of three was detected by 
alpha-fetoprotein plus free beta-human chorionic gonadotropin. By adding 12 
additional cases of fetal Down syndrome, 12 of 15 (80%) were screen positive 
with triple marker and nine of 15 (60%) were screen positive with 
alpha-fetoprotein plus free beta-human chorionic gonadotropin.
CONCLUSION: The detection rate of fetal Down syndrome was greater by use of a 
triple marker screen than when using alpha-fetoprotein plus free beta-human 
chorionic gonadotropin. Our data do not support the claims of other studies that 
suggest that alpha-fetoprotein plus free beta-human chorionic gonadotropin is 
superior to triple markers.