RACE-ETHNICITY-SPECIFIC VARIATION IN MULTIPLE-MARKER BIOCHEMICAL SCREENING - ALPHA-FETOPROTEIN, HCG, AND ESTRIOL

Objective: To identify any race-ethnicity-specific differences in seru m alpha-fetoprotein (AFP), hCG, and unconjugated estriol (E3) levels i n women between 14 and 21 weeks' gestation. Methods: Data from the 3-y ear period 1992-1994 were analyzed from 208,257 women who had AFP scre ening, of whom 155,142 also had hCG and 62,121 also had E3 screened, b etween 14 and 21 weeks' gestation. Subjects were categorized into four groups: white, black, Asian, and Hispanic. Results: There was a consi stent pattern of analyte differences across gestational ages. Levels f or AFP were generally higher in Asian and black women than in Hispanic and white women (median AFP at 16 weeks-31.2, 30.9, 27.4, 27.3, respe ctively), and levels of hCG and E3 were highest in Asians (hCG at 16 w eeks-34.7, 30.3, 28.2, 26.8, respectively). Weight correction for AFP, hCG, and E3 levels did not compensate for the ethnic differences. Con clusions: Because hCG and E3 demonstrate the same general pattern of d ifferences as AFP among ethnic groups, averaging values for all ethnic groups tends inappropriately to lower calculated Down syndrome risks for black and Asian women. Additionally, the slopes of the curves are not parallel, such that separate data bases are preferable to multipli cative correction factors. Separate data bases should be used in labor atories with volume sufficient to permit the establishment of race-eth nicity-specific regressions. Use of separate data bases should result in more accurate screening. Copyright (C) 1997 by The American College of Obstetricians and Gynecologists.