AChE is performed on an amniotic fluid sample to diagnose fetal open neural tube defects and some ventral wall defects. Please note that AChE will be reflexively performed and billed when AFAFP is elevated and/or gestational age is out of range of normative values.
Diagnose fetal open neural tube defects and some ventral wall defects.
Immunochemiluminometric assay (ICMA); acrylamide gel electrophoresis; isoelectric focusing
2 mL (discard first 2 mL)
Small AFP tube
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.
Patient's gestational age must be at least 12 weeks for interpretation of α-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.
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
Note: AChE will be reflexively performed and billed when amniotic fluid α-fetoprotein (AFAFP) is elevated and/or gestational age is out of range of normative values.