ELEVATED AMNIOTIC-FLUID ALPHA-FETOPROTEIN WITHOUT NEURAL-TUBE DEFECTS

Abstract A single-blind study involving amniotic-fluid samples from 214 pregnancies of known outcome confirms that an electrophoretically distinct isoenzyme of acetylcholinesterase is associated with fetal open neural tube defects. Furthermore, only one of 13 amniotic-fluid samples with false-positive results for alpha-fetoprotein showed the characteristic isoenzyme, indicating that qualitative acetylcholinesterase assessment can decrease the proportion of false positives from the alpha-fetoprotein assay. We have also identified this characteristic isoenzyme in amniotic fluids from pregnancies in which other serious fetal defects occurred. A detailed electrophoresis protocol for identifying this characteristic isoenzyme is described.

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Concanavalin A binding of alpha-fetoprotein in amniotic fluid as an aid in the diagnosis of neural tube defects.

Clinical Chemistry ◽

10.1093/clinchem/27.10.1658 ◽

1981 ◽

Vol 27 (10) ◽

pp. 1658-1660 ◽

Cited By ~ 8

Author(s):

P K Buamah ◽

P Taylor ◽

A M Ward

Keyword(s):

Spina Bifida ◽

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Concanavalin A ◽

Gestational Age ◽

Alpha Fetoprotein ◽

Normal Outcome ◽

Fetal Malformations ◽

Open Spina Bifida

Abstract Concanavalin A nonreactive alpha-fetoprotein was determined in samples of amniotic fluid from 16 abnormal pregnancies complicated by anencephaly (7), open spina bifida (6), intra-uterine death (1), anencephaly with exomphalos (1), or open spina bifida with exomphalos (1), and in amniotic fluid from 50 normal pregnancies with gestational age between 13 and 24 weeks. In all 16 cases with fetal malformations, the proportion of nonreactive alpha-fetoprotein was significantly decreased (median 5.3%) as compared with amniotic fluid from pregnancies with a normal outcome (median 39.7%). The results confirm that this measurement is useful in the diagnosis of neural tube defects, especially when the concentration of alpha-fetoprotein in amniotic fluid is normal or only slightly above normal and gestational age is uncertain.

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Gender-adjusted multiples of the median in amniotic fluid alpha-fetoprotein-screening for neural-tube defects halve false-positive rate without affecting detection rate

Ultrasound in Obstetrics and Gynecology ◽

10.1046/j.1469-0705.2001.abs23-4.x ◽

2001 ◽

Vol 18 ◽

pp. F58-F58

Author(s):

P. Kozlowski ◽

A. J. Knippel ◽

R. Stressig

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

False Positive ◽

Detection Rate ◽

False Positive Rate ◽

Alpha Fetoprotein ◽

Positive Rate

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Evaluation of an enhanced luminescence assay for alpha-fetoprotein.

Clinical Chemistry ◽

10.1093/clinchem/32.11.2066 ◽

1986 ◽

Vol 32 (11) ◽

pp. 2066-2069 ◽

Cited By ~ 5

Author(s):

R John ◽

R Henley ◽

D Shankland

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Maternal Serum ◽

Regression Equation ◽

Alpha Fetoprotein ◽

Reliable System ◽

Analytical Recovery ◽

Luminescence Assay ◽

Enhanced Luminescence

Abstract We evaluated a two-site enhanced luminescence immunoenzymometric assay (Amerlite; Amersham International) for alpha-fetoprotein (AFP) in maternal serum and amniotic fluid. The assay is rapid, involving two incubations totalling 4 h. The working range of the assay for serum AFP is 5.5 to 750 kilo-int. units/L (CV less than 10%), with a sensitivity of detection of 0.2 kilo-int. unit/L. The regression equation for the Amerlite assay (y) and our in-house RIA procedure (x) was y = 0.816x + 2.9 (n = 142, r = 0.96). Analytical recovery of added AFP (code 72/227) at three concentrations was 86.7%. Serum AFP concentrations were measured at 15 to 18 weeks of gestation in subjects with normal pregnancies and in subjects whose pregnancies resulted in open neural tube defects; all of the latter had serum AFP concentrations greater than 2.5 multiples of the median. We find the Amerlite system to be an efficient, reliable system for screening for open neural tube defects without use of hazardous radioactive labels.

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