Effect of Hispanic ethnicity on interpretation of maternal serum screening.

Maternal serum concentrations of alpha-fetoprotein (MSAFP), unconjugated estriol (uE3) and human chorionic gonadotropin (hCG) were measured in the sera of 3,046 Hispanic women and of 15,154 Caucasian women from gestational weeks 14 through 20 between January 1990 and December 1995. Median values for analytes were calculated for each gestational week and the two ethnic groups compared. Our findings indicate that the median values for Hispanics are lower for MSAFP and hCG, but higher for estriol. These differences are not accounted for by differences in median weights of the two ethnic groups. Although these results would suggest that Hispanic women at risk for a fetus with a neural tube defect (NTD) may be missed when cut-offs derived from a Caucasian population are used, in fact, that was not the case in our screening population. However, a disproportionate number of Hispanic women may be identified with an abnormal serum screening test unrelated to a risk for neural tube defects. This does not infer that detection rates are different across different ethnic groups since other factors are involved. Adjustment of medians for Hispanic ethnicity may have a small but significant effect, especially with regard to low values.