[Second trimester maternal serum screening for Down's syndrome in mainland China: a multi-center prospective study].
ABSTRACT To evaluate the performance characteristics of the second trimester double-marker test for the detection of fetal Down's syndrome in mainland China.
This prospective national multi-centered study used alpha-fetoprotein (AFP) and free beta-subunit of human chorionic gonadotrophin (free beta-hCG) as the serum markers. From May 2004 to September 2006, 11 centers participated in the collection and analysis of maternal serum AFP and free beta-hCG between 14 and 20(+6) weeks of pregnancy. The screening results were calculated using the standard algorithm based on the standard database provided with the analytic software. Patients with an increased risk of Down's syndrome pregnancy (> or = 1/270) were offered genetic amniocentesis. Outcomes of all pregnancies were obtained.
A total of 66 132 singleton pregnancies were included in the study. The median maternal age was 27 years. At a cut-off of 1 in 270, the detection rate (DR) based on a Caucasian database was 72% corresponding to a false positive rate (FPR) of 5%, and the DR based on the Chinese database was raised to 76% corresponding to an FPR of 5%.
The double-marker test using AFP and free beta-hCG is an effective screen strategy for second-trimester detection of fetal Down's syndrome in mainland China. Ethnic variance exists between the Caucasian and Chinese populations. The accuracy of screening is increased by the use of race-specific medians.
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ABSTRACT: The aim of the present study was to establish Thai-specific reference ranges of triple markers for fetal Down syndrome as a function of gestational age as well as weight correction models and to compare the false positive rates when using Thai-specific model relative to Caucasian-specific model. A total of 993 normal Thai pregnant women were determined for mid-trimester serum levels of alpha-fetoprotein (AFP), free-beta human chorionic gonadotropin (hCG), and unconjugated estriol (uE3), using DefiaXpress system (Perkin Elmer, Waltham, MA, USA). The models of Thai-specific medians for AFP, b-hCG, and uE3, as well as the models for weight correction were derived and the normal reference ranges were constructed. The best fitted equation for AFP, b-hCG and uE3 are as follows: predicted median = 2.675 × 10((0.153 × GA in week)), r = 0.979; 10((-0.717 + 57.487/GA in week)) , r = 0.991; and 10((5.678-69.346/GA) (in) (week)), r = 0.99, respectively. The models were properly applied to another group of 302 Thai women, signifying that they were reliable models. The weight-adjusted gestation-specific medians derived from Caucasian models were significantly higher than those based on Thai models and the false positive rate could be reduced from 10 to 7.1% when Thai models were applied. Thai reference ranges of triple screen markers as a function of gestational age as well as weight correction models have been established. The Caucasian reference range, even after weight correction, gives a positive rate that is much higher than that it should be, strongly suggesting the need for ethnicity-specific medians.Journal of Obstetrics and Gynaecology Research 03/2012; 38(4):686-91. · 0.84 Impact Factor