COMPARISON OF MULTIPLE-MARKER SCREENING WITH AMNIOCENTESIS FOR THE DETECTION OF FETAL ANEUPLOIDY IN WOMEN GREATER-THAN-OR-EQUAL-TO-35 YEARSOLD

OBJECTIVE: Our purpose was to compare the multiple-marker screening te st with elective amniocentesis for the detection of fetal Down syndrom e and other aneuploidies in women aged greater than or equal to 35. ST UDY DESIGN: Our database included the multiple-marker screening test ( maternal serum alpha-fetoprotein, human chorionic gonadotropin, unconj ugated estriol, and maternal age) and genetic amniocentesis results fr om 1942 women aged greater than or equal to 35. A Down syndrome risk g reater than or equal to 1:190 was considered screen positive. An algor ithm 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 det ection 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, trisom y 22, and trisomy 18. CONCLUSIONS: The multiple-marker screening test fails to detect approximately 39% of all fetal aneuploidies in women a ged greater than or equal to 35. These data should be provided to wome n considering prenatal diagnosis so that they can make an informed dec ision regarding the multiple-marker screening test versus amniocentesi s for advanced maternal age.