Edward J. Cook

Maternal serum Down syndrome screening: Unconjugated estriol is not useful

Study of 41 known Down syndrome cases and 441 matched controls did not confirm earlier reports that low unconjugated estriol levels can be used to detect fetal Down syndrome. Hence the obstetric community should exercise caution in using unconjugated estriol levels as a marker in prenatal Down syndrome screening.

Free β-Chorionic Gonadotropin: A Cross-Reactivity Study of Two Immunometric Assays Used in Prenatal Maternal Serum Screening for Down's Syndrome

We have evaluated the cross-reactivity characteristics of two distinct immunometric assays for the measurement of free β-human chorionic gonadotropin (free β). These maternal serum assays have been used in the initial studies which evaluated free β as a marker in the prenatal detection of Downs syndrome. It has been suggested that free β assays are subject to substantial potential for cross-reactivity. To confirm that free β was the analyte responsible for enhanced detection efficiency both non-competitive and competitive cross-reactivity evaluations were undertaken. These studies demonstrated acceptably small cross-reactivity to other glycoprotein hormones or their β components. We conclude that properly designed free β assays will provide specific analyte measurement and improved detection efficiency in Downs syndrome screening.

Maternal serum α-fetoprotein screening

Maternal serum α-fetoprotein levels are higher in black women. Misinterpretation of maternal serum α-fetoprotein screening results can subject black gravid women to unnecessary invasive diagnostic procedures and their calculable risks. Screening errors for black women can result from the use of normative data bases established with maternal serum samples drawn from other racial groups or the use of such data bases in conjunction with a published correction factor. Because the incidence of open neural tube defects is lower for blacks than for others, excessive false positive results for blacks (estimated to be 8817 to 28,215 cases annually) would be a pernicious misapplication of maternal serum α-fetoprotein screening. We address the problem outlined above and recommend independently developed, valid, normative data bases.