Amniotic Fluid Alpha-Fetoprotein (AFAFP) Testing
AFP, Amniotic Fluid; Alpha-Fetoprotein (AFP), Amniotic Fluid; Amniotic Fluid AFP;
Measurement of amniotic fluid AFP. Samples with AFP values ≥2.0 MoM will reflex to detection of acetylcholinesterase and fetal hemoglobin.
Include the gestational age by ultrasound and/or last menstrual period (LMP) on the request form on the date of draw of the sample. The patient's gestational age must be at least 12 weeks for interpretation of α-fetoprotein. Note that AChE false-positive and false-negative results are more frequent at gestational ages less than 13 weeks. Optimal gestational age is 14 to 18 weeks.
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.
Maintain specimen at room temperature.
Causes for Rejection
Specimen not amniotic fluid; gross contamination of amniotic fluid with maternal or fetal blood; quantity not sufficient for analysis
Analysis of mid-trimester amniotic fluid for detection of open neural tube defects and ventral wall defects
Immunochemiluminometric assay (ICMA)
AFAFP analysis is used to screen for fetal open neural tube defects and abdominal wall defects. Please note: AChE will be reflexively performed and billed when AFAFP is elevated and/or gestational age is out of range of normative values. AFAFP results are reported together with the chromosome analysis unless chromosome analysis is abnormal.