First trimester combined screening for Down′s Syndrome with NT, Free-βhCG and PAPP-A

Objective To explore the sensitivity of using NT, combined with serum biochemical markers (Free-βhCG，PAPP-A) for Down′s Syndrome screening in early stage of pregnancy. Methods Collect pregnant women aged 17-45 years old voluntary antenatal screening in our hospital from March 2009 to October 2010, a total of 11882 cases.Serum Free-βhCG and PAPP-A were measured NT value was determined by ultrasound at 11-13w+6d of gestation.Calculating combined screening (NT, Free-βhCG, PAPP-A), and serum integrated screening (Free-beta hCG, PAPP-A) risk, respectively, using the risk calculation software for the same person. Results Early pregnancy screening was performed in 11 882 patients, 18 had a fetus with Down′s syndrome, a rate of 0.15%.The detection rates of Down′s syndrome in combined screening and serum integrated screening were 83.3% and 72.2% respectively.The specificities were 98.4% and 97.3% and detection efficiency were 7.18%, 3.90% respectively.Areas under the curve (AUCs) of first-trimester combined screening and serum integrated screening were 0.975（95% CI:0.943,1.007）, 0.901 (95% CI:0.789, 1.013) respectively. Conclusion In early stage of pregnancy, combined screening for Down′s syndrome has higher sensitivity and specificity than serological screening, has higher detection rate in the same false-positive rate case, which can effectively reduce the pregnant women to receive invasive puncture.（Chin J Lab Med，2012,35：932-935） Key words: Pregnancy trimester;  first; Down syndrome; Prenatal diagnosis; Nuchal translucency measurement