Acetylcholinesterase (AChE) Testing

Test Details


Diagnose fetal open neural tube defects and some ventral wall defects.

Special Instructions

Patient's gestational age must be at least 12 weeks for interpretation of a-fetoprotein. State gestational age by ultrasound and/or last menstrual period (LMP) on the request form. Note that AChE false-positive and false-negative results are more frequent at gestational ages of less than 13 weeks. Optimal gestational age for detection of AChE is 14 to 18 weeks.


Immunochemiluminometric assay (ICMA); acrylamide gel electrophoresis; isoelectric focusing

Additional Information

Note: AChE will be reflexively performed and billed when amniotic fluid a-fetoprotein (AFAFP) is elevated and/or gestational age is out of range of normative values.

Specimen Requirements

Information on collection, storage, and volume


Amniotic fluid


2 mL (discard first 2 mL)


Small AFP tube

Causes for Rejection

Specimen found not to be amniotic fluid; gross contamination of amniotic fluid with maternal or fetal blood; quantity not sufficient for analysis


Avoid contamination of amniotic fluid with maternal or fetal blood. As little as one drop of fetal blood can cause false-positive results during assay of amniotic fluid. Amniotic fluid should be collected by the attending physician.