Comparison of multiple-marker screening with amniocentesis for the detection of fetal aneuploidy in women > or = 35 years old.

OBJECTIVE

Our purpose was to compare the multiple-marker screening test with elective amniocentesis for the detection of fetal Down syndrome and other aneuploidies in women aged > or = 35.

STUDY

DESIGN

Our database included the multiple-marker screening test (maternal serum alpha-fetoprotein, human chorionic gonadotropin, unconjugated estriol, and maternal age) and genetic amniocentesis results from 1942 women aged > or = 35. A Down syndrome risk > or = 1:190 was considered screen positive. An algorithm to detect trisomy 18 was also used.

RESULTS

The multiple-marker screening test Down syndrome screen-positive rate was 26.1% (507/1942). The Down syndrome detection rate was 75% (33/44); the trisomy 18 detection rate was 75% (3/4). However, the multiple-marker screening test detection rate for all aneuploidies was only 61%. Missed aneuploidies included trisomy 21, sex chromosome abnormalities, trisomy 13, trisomy 22, and trisomy 18.

CONCLUSIONS

The multiple-marker screening test fails to detect approximately 39% of all fetal aneuploidies in women aged > or = 35. These data should be provided to women considering prenatal diagnosis so that they can make an informed decision regarding the multiple-marker screening test versus amniocentesis for advanced maternal age.