MATERNAL SERUM ALPHA-FETOPROTEIN AND DIMERIC-INHIBIN-A DETECT ANEUPLOIDIES OTHER THAN DOWN-SYNDROME

OBJECTIVE: Our purpose was to determine whether the combination of mat ernal serum alpha-fetoprotein, free human chorionic gonadotropin-beta, dimeric inhibin A, and maternal age detects aneuploidies other than D own syndrome. STUDY DESIGN: We retrieved stored serum from pregnancies complicated by aneuploidies other than Down syndrome from 1988 to 199 7 (n = 55, mean maternal age 35.2 +/- 5.6 years). alpha-fetoprotein le vels were obtained from our database, and free human chorionic gonadot ropin-beta and dimeric inhibin A levels were measured in the thawed se rum 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 cuto ff values. RESULTS: In the 3-analyte test 58% (32/55) of all aneuploid ies were detected with use of both the Down syndrome protocol at a scr een-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-fetoprote in and dimeric inhibin A, with both the Down syndrome protocol (screen positive cutoff value 1:300) and the trisomy 18 algorithm: 12 of 13 t risomy 18 (92%), 9 of 17 Turner's syndrome (53%), 10 of 17 other sex c hromosome aneuploidies (59%), 1 of 1 trisomy 22 (100%), and 5 of 7 tri somy 13 (71%). CONCLUSIONS: The combination of maternal serum alpha-fe toprotein, dimeric inhibin A, and maternal age detects autosomal triso mies other than Down syndrome at a rate superior to that of the tradit ional analyte combination.