The Application Of Ultrasonographic Examination Of Fetal Nuchal Translucency, Nasal Bone, Which Combined Measurement Maternal Serum Free Beta-hcg, And Pregnancy-associated Plasma Protein A For Screening Down's Syndrome In The First-trimester.

Objective:Use NT,NB which associated with maternal serum PAPP-A,β-HCG for screening Down's syndrome, in order to approach it's sensitivity and specificity,false positive rate and false negative rate,positive and negative predicted value.Method:Choose 671 pregnant women(singleton pregnancies) at 11-14weeks who visit out-patient clinic for antenatal examination in January 1st to September 30th in 2010 as A group, measure fetal NT,nasal bone through ultrasound, and associate with maternal serum PAPP-A,β-HCG for screening Down's syndrome. Then when fetuses grow to 16-20weeks as B group, exam the concentration of maternal serumβ-HCG,AFP,μE3 for screening Down's syndrome of mid trimester of pregnancy. High risk pregnant women of screening undertake prenatal diagnosis. Compare two groups with sensitivity and specificity,false positive rate and false negative rate,positive and negative predicted value, and Youden Index. Final diagnose Down's syndrome are rejected. Then calculate the mean,standard deviation,95% limit reference value,2.5 percentile of 11-14weeks fetal nasal bone in normal Chinese. Result:20 pregnant women is high risk in group A,51 pregnant women is high risk in group B. 18 cases of high risk in group A are included in group B who are high risk. And 2 cases of high risk in group A are included in group B who are low risk. Add all of high risk cases(53 cases) in group A and B, after agreement, final diagnose Down's syndrome by prenatal diagnosis are 10.These 10 cases are all included in group A of high risk cases,2 cases are missed in group B of high risk cases. No missed diagnosis of all low risk cases in postpartum follow-up. In group A, sensitivity is 100%, specificity is 98.49%, the false positive rate is 1.51%, false negative rate is 0, positive predicted value is 50%, negative predicted value is 100%, Youden Index is 0.9849. In group B, sensitivity is 80%, specificity is 93.49%, the false positive rate is 6.51%, false negative rate is 20%, positive predicted value is 15.69%, negative predicted value is 99.68%, Youden Index is 0.7349. Compare two groups' sensitivity, using Fisher's Exact Test, P= 0.757>0.05, it's no statistics signification. Compare two groups'specificity,χ2=0386, P=0.535>0.05, it's no statistics signification. Compare two groups' false positive rate,χ2=19.767, P= 0.000<0.05, it have statistics signification. Compare two groups'false negative rate, using Fisher's Exact Test, P= 0.481>0.05, it's no statistics signification. Compare two groups' positive predicted value,χ2=4.82, P=0.028<0.05, it have statistics signification. Compare two groups' negative predicted value,χ2=0.002, P=0.968>0.05, it's no statistics signification. The mean of 11-14weeks fetal nasal bone in normal Chinese is 2.847 mm, the standard deviation is 0.794 mm,95% limit reference value is 2.053～3.641mm,2.5 percentile is 1.598 mm. Conclusion:It is a higher sensitivity and positive predicted value, lower false positive rate, security and reliability way which combined measurement of fetal nuchal translucency, nasal bone by ultrasound, maternal serum free beta-HCG, and pregnancy-associated plasma protein A for screening Down's syndrome in the first-trimester. It is worth extending and utilizing.