Maternal serum alpha-fetoprotein and dimeric inhibin A detect aneuploidies other than Down syndrome.

OBJECTIVE

Our purpose was to determine whether the combination of maternal serum alpha-fetoprotein, free human chorionic gonadotropin-beta, dimeric inhibin A, and maternal age detects aneuploidies other than Down syndrome.

STUDY DESIGN

We retrieved stored serum from pregnancies complicated by aneuploidies other than Down syndrome from 1988 to 1997 (n = 55, mean maternal age 35.2 +/- 5.6 years). Alpha-fetoprotein levels were obtained from our database, and free human chorionic gonadotropin-beta and dimeric inhibin A levels were measured in the thawed serum with use of commercial assays. Analyte values were used in both 3-analyte and 2-analyte multiple-marker screening tests; detection rates were determined at several different Down syndrome risk-positive cutoff values.

RESULTS

In the 3-analyte test 58% (32/55) of all aneuploidies were detected with use of both the Down syndrome protocol at a screen-positive risk cutoff value of 1:300 (false-positive rate 17%) and a novel trisomy 18 screening algorithm. However, 67% (37/55) detection was obtained with use of the 2-analyte combination of alpha-fetoprotein and dimeric inhibin A, with both the Down syndrome protocol (screen positive cutoff value 1:300) and the trisomy 18 algorithm: 12 of 13 trisomy 18 (92%), 9 of 17 Turner's syndrome (53%), 10 of 17 other sex chromosome aneuploidies (59%), 1 of 1 trisomy 22 (100%), and 5 of 7 trisomy 13 (71%).

CONCLUSIONS

The combination of maternal serum alpha-fetoprotein, dimeric inhibin A, and maternal age detects autosomal trisomies other than Down syndrome at a rate superior to that of the traditional analyte combination.