There is a 30% pickup of congenital abnormality with maternal age and AFP.
The result is, in an average protocol, reported as high if the level, represented as a multiple of median, is 2.4 times normal i.e. if the risk is 1 in 200 or more that there is an abnormality.
If AFP concentration is raised in the maternal serum, the pattern of cholinesterase enzymes on polyacrylamide gel electrophoresis is often helpful. Open neural tube defects and half of all anterior abdominal wall defects will have a second band.
Last reviewed 01/2018