Amniotic fluid contains acetyl cholinesterase enzyme. What is the diagnosis ?
Open spina bifida
Gastroschisis
Omphalocele
Osteogenesis imperfecta
Amniotic fluid Acetylcholineesterase level is elevated in open neural tube defect:

It has a better diagnostic value than AFP.
In case of suspected neural tube defect, on Amniocentesis, if amniotic fluid AFP levels are raised but Acetylcholinesterase levels are normal, patient should be reassured that elevated AFP levels are probably caused by fetal blood contamination but, if acetyl cholinesterase is also elevated along with AFP it is indicative of NTD.
It also helps to distinguish between neural tube defect and abdominal wall defects (both of which cause elevated MSAFP):

– Acetyl cholinesterase is raised in open NTD, but is low in abdominal wall defects.
– In patients with NTD, the ratio of acetylcholinesterase to butyrlcholinesterase levels is 0.14 or more. In case of abdominal wall defects this ratio is less than 0.14.