Determination of Amniotic Fluid Alpha-fetoprotein and Acetylcholinesterase for Prenatal Diagnosis of Open Neural Tube Defects

Oh, B H; Lee, J M; Lee, K H; Kwon, M S

Abstract

OBJECTIVE
For prenatal diagnosis of open neural tube defects [ONTDs] in pregnant women by the determination of alpha-fetoprotein [AFP] and acetylcholinesterase [AChE] in amniotic fluid [AF].
METHODS
Median values and upper cut-off levels of AF AFP were determined by radioimmunoassay in 1,710 pregnancies between 15 and 25 weeks` gestation. When AF AFP value was above 2.0 multiples of median [MoM], AF AChE was examined by native gel electrophoresis with activity staining.
RESULTS
Sixty one cases [5.4%, 61/1,137] had elevated level of AF AFP [> or = 2.0 MoM]. ONTDs, ventral wall defect, and fetal demise were detected in 14 of them [23%, 14/61] by level II ultrasonography or gross finding of abortus. All but one case had positive or weakly positive AChE band on the gel. There were 7 cases with positive AChE including open spina bifida [6] and anencephaly [1]. Six cases with weakly positive AChE showed gastroschisis [4], omphalocele [1] and fetal demise [1]. Only one case with negative AChE was turned out to be gastroschisis. The remnant 47 cases [77%, 47/61] with normal outcome but elevated AFP had negative AChE results. The sensitivity of AF AFP and that of AChE for ONTD detection were comparable [100% vs 100%]. However, the positive predictive values of these analyses were quite different [11.5% vs 100%].
CONCLUSION
Determination of AF AChE along with AF AFP values will provide reliable information for the prenatal diagnosis of open fetal malformation such as ONTDs and ventral wall defects in pregnant women during the second trimester.