Alpha-Fetoprotein and Acetylcholinesterase, Amniotic Fluid with Reflex to HbF

Laboratory assay overview

Alpha-fetoprotein (AFP) utility in the early detection of fetal open neural tube defects (NTD) has been widely confirmed. The severity of a neural tube defect can range from moderate, such as spina bifida, to severe and non-life-compatible, such as anencephaly. Acetylcholinesterase(AChE) is an enzyme that hydrolyzes the neurotransmitter acetylcholine. In a fetus with an open neural tube defect, AChE leaks directly into the amniotic fluid from fetal CSF, causing unexpectedly high levels of amniotic fluid AChE. However, a major cause of borderline amniotic fluid AFP elevations and/or false positive AChE results is contamination of the sample with fetal blood. Therefore, reflex testing for the presence of fetal hemoglobin (HbF) should be performed on samples with elevated AFP results, and in particular when acetylcholinesterase is weak positive or not detected at all. It is important to remember that many fetal anomalies, including neural tube defects and ventral wall defects, may also lead to fetal bleeding.