Screening effectiveness of the double test and the triple test of Down syndrome in second trimester pregnancy

Objective:To compare the screening effectiveness of the double test and the triple test of Down syndrome in second trimester pregnancy,evaluate the value of unconjugated estriol(uE3) in the prenatal screening.Methods:The levels of human chorionic gonadotropin freeβsubunit(free β-HCG),alpha-fetoprotein(AFP) and uE3 from serum samples of singleton pregnant women receiving the prenatal screening and the frozen stored serum samples of Down syndrome pregnancies were detected by time-resolved fluoroimmunoassay.The values at risk of double test(AFP+ free β-HCG) and triple test(AFP+ free β-HCG+uE3) were calculated by LifeCycle software respectively.The detection rate and false positive rate of the double test and the triple test were compared.Results:Among 1 078 prenatal screening cases and 10 frozen serum samples of Down syndrome pregnancies,when the cut-off value at risk was set at 1:270,the double test and the triple test had the same detection rate(66.7%),and the false positive rates of the double test and the triple test were 7.2% and 4.6%,respectively;when the cut-off value at risk was set at 1:380,the detection rate of the triple test(91.7%) was higher than that of the double test(75%),and the false positive rates of the double test and the triple test were 10.1% and 7.5%,respectively.Conclusion:The triple test is an more effective screening option for Down syndrome screening than the double test.It is necessary to establish a proper cut-off value for the local population to improve the effectiveness of screening.