Amniotic fluid acetylcholinesterase: a retrospective and prospective study of the qualitative method.

After retrospective evaluation with stored samples, the qualitative acetylcholinesterase (AChE) test has been used prospectively in conjunction with alpha-fetoprotein (AFP) assay on 986 amniotic fluid specimens received in this laboratory during 1980. The main value of AChE is in classifying fluids in which the AFP level is near the threshold between normal and abnormal. Among abnormal pregnancies with raised AFP levels, neural-tube defects can generally be distinguished from other abnormalities by careful appraisal of the AChE gel pattern, but confirmation of these other fetal abnormalities may require high resolution diagnostic ultrasonography and perhaps fetoscopy. Neural-tube defects with false negative AFP levels can be detected by AChE, but AChE gives occasional false positives so that it cannot be relied on in isolation for the diagnosis of neural-tube defects.