Marker of open neural tube defect? (AIPG 11)
|A||Amniotic fluid acetylcholine esterase|
|B||Amniotic fluid acetylcholine kinase|
|C||Amniotic fluid HCG|
|D||Amniotic fluid pseudoacetylcholine esterase|
Amniotic fluid acetylcholine esterase
If present after 14 weeks of gestation, amniotic fluid acetylcholinesterase is considered direct evidence of an open neural tube defect.
1. Normal range by method:
a. Polyacrylamide gel electrophoresis: Negative
b. AE-2 immunoassay: Negative
c. Inhibition assay: 5.17 ± 2.63 milliunits/mL (5.17 ± 2.63 units/L)
2. In the screening of Downs Syndrome:
3. May see Nuchal translucency (be able to see through the tissue just behind the skull) from ultrasound nuchal scan.
4. Absent nasal bones on ultrasound. (Limited as some ethnic groups contain no nasal bones).
a. If they see any of these they do a number of different tests:
5. Triple test
a. 14-21 weeks: AFP, unconjugated oestriol (uE3), and hCG together with maternal age.
6. Nuchal Translucency Scan (NT scan)
a. 11-136 weeks: measurement of the fold of skin on the back of the foetal neck (Nuchal Translucency) together with the maternal age.
7. Quadruple test
a. 14-21 weeks: AFP, uE3, free β-hCG (or total hCG) and inhibin-A together with maternal age.
8. Combined test
a. 10-136 weeks: NT measurement with free β-hCG, PAPP-A and maternal age.
9. Integrated test - this is the most accurate and reliable. This combines maternal age with the following:
a. 1. 11-14 weeks: NT + PAPP-A
b. 2. 15-22 weeks: AFP + hCG + uE3 + Inhibin