Elevated second-trimester dimeric inhibin A levels identify Down syndrome pregnancies.
OBJECTIVE
Our purpose was to determine whether second-trimester dimeric inhibin A levels distinguish Down syndrome pregnancies from euploid pregnancies.


METHODS
With use of a commercially available enzyme-linked immunosorbent assay (Serotec, Oxford) inhibin A medians were established in stored sera from 40 to 50 euploid pregnancies at each week of gestation from 14 to 20 weeks and from 33 Down syndrome pregnancies. Maternal serum alpha-fetoprotein, unconjugated estriol, and human chorionic gonadotropin levels measured in each sample before storage were retrieved. The performance of inhibin A in the multiple-marker screening test was evaluated.


RESULTS
The mean inhibin A multiple of the median was significantly higher in the Down syndrome group than in the euploid group (2.84 +/- 2.0 vs 1.22 +/- 1.0, p = 0.0001). An inhibin A level > or = 1.6 multiples of the median identified 70% of all Down syndrome pregnancies at a false-positive rate of 22%. Replacing estriol with inhibin A in the multiple-marker screening test resulted in a higher Down syndrome detection rate at a lower screen-positive rate.


CONCLUSIONS
Elevated second-trimester maternal serum inhibin A levels identify Down syndrome pregnancies; replacing estriol with inhibin A in the multiple-marker screening test improves test performance.
Wenstrom
K D
KD
Department of Obstetrics and Gynecology, University of Alabama at Birmingham 35233-7333, USA.
Owen
J
J
Chu
D C
DC
Boots
L
L
D000328:Adult; D006063:Chorionic Gonadotropin / Q000097:blood; D019281:Dimerization; D004314:Down Syndrome / Q000175:diagnosis*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007265:Inhibins / Q000097:blood*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011296:Prenatal Diagnosis; D000509:alpha-Fetoproteins / Q000032:analysis
D006063:Chorionic Gonadotropin; D000509:alpha-Fetoproteins; D007265:Inhibins