Neural tube defects and elevated homocysteine levels in amniotic fluid

The measurement of low levels of cholinesterase or acetylcholinesterase by the Ellman method requires correction for a non-enzymatic increase in absorption at 412 mμ that is due both to non-enzymatic hydrolysis of the acetylthiocholine substrate and to modification of the colour reagent. The rate of increase in absorption is dependent on temperature and pH. Addition of an acidic solution of lysivane to the assay solution for selective measurement of amniotic fluid acetylcholinesterase gives rise to a shift in pH; the use of methanol is suggested as an easier method of dissolving the inhibitor and does not affect the pH of the assay, obviating any need to redetermine the background absorption. There is, however, no improvement in ability of the method to predict pregnancies associated with neural-tube defects.

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Catecholamine metabolites in amniotic fluid from fetuses with neural tube defects

Prenatal Diagnosis ◽

10.1002/pd.1970010212 ◽

1981 ◽

Vol 1 (2) ◽

pp. 157-159 ◽

Cited By ~ 1

Author(s):

H. Lagercrantz ◽

B. Sjöquist

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Catecholamine Metabolites

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Acetylcholinesterase and fetal malformations: modified qualitative technique for diagnosis of neural tube defects.

Clinical Chemistry ◽

10.1093/clinchem/27.1.61 ◽

1981 ◽

Vol 27 (1) ◽

pp. 61-63 ◽

Cited By ~ 27

Author(s):

J E Haddow ◽

M E Morin ◽

M S Holman ◽

W A Miller

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

False Positive ◽

Alpha Fetoprotein ◽

Blind Study ◽

Fetal Malformations ◽

Qualitative Technique ◽

Single Blind ◽

Positive Results

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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Quantification of the D2-Glycoprotein in Amniotic Fluid and Serum from Pregnancies with Fetal Neural Tube Defects

Journal of Neurochemistry ◽

10.1111/j.1471-4159.1983.tb04751.x ◽

1983 ◽

Vol 41 (2) ◽

pp. 363-366 ◽

Cited By ~ 28

Author(s):

Susanne Ibsen ◽

Vladimir Berezin ◽

Bent Nørgaard-Pedersen ◽

Elisabeth Bock

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects

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Amniotic fluid fibrinolytic system in fetal neural tube defects

Prenatal Diagnosis ◽

10.1002/pd.1970030212 ◽

1983 ◽

Vol 3 (2) ◽

pp. 145-149

Author(s):

Michael Legge

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Fibrinolytic System

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

The Lancet ◽

10.1016/s0140-6736(75)91024-7 ◽

1975 ◽

Vol 306 (7945) ◽

pp. 1141 ◽

Cited By ~ 17

Author(s):

N.J. Leschot ◽

P.E. Treffers

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Alpha Fetoprotein

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ROLE OF AMNIOTIC FLUID ACETYLCHOLINESTERASE IN SCREENING FOR NEURAL TUBE DEFECTS

The Lancet ◽

10.1016/s0140-6736(81)91716-5 ◽

1981 ◽

Vol 317 (8216) ◽

pp. 391 ◽

Cited By ~ 2

Author(s):

Ray Garry ◽

John Atkins ◽

S.J. Richardson ◽

Brian Webb

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects

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Antenatal Diagnosis of Neural Tube Defects Using a Coated Bead Immunoassay for Acetylcholinesterase in Amniotic Fluid

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456328802500515 ◽

1988 ◽

Vol 25 (5) ◽

pp. 569-576 ◽

Cited By ~ 3

Author(s):

Shobhna Mehta ◽

Kevin Spencer

Keyword(s):

Amniotic Fluid ◽

Neural Tube ◽

Neural Tube Defects ◽

Colorimetric Method ◽

False Positives ◽

Operator Technique ◽

Good Precision ◽

Red Cell Membrane ◽

Coated Bead ◽

Bead Immunoassay

The development and validation of a coated bead immunoassay for amniotic fluid acetylcholinesterase is outlined. The assay has good precision (between assay CV of 6·8% within the normal range), and is linear up to 250 arbitrary units/L. The clinical validity of this assay has been assessed using a panel of amniotic fluid samples from normal and abnormal pregnancies. At an assay cut off level of 200 arbitrary units/L, all cases of neural tube defect-affected pregnancies were identified and the number of false positives was very small. False positives resulted from severe blood staining of the amniotic fluid. Since the monoclonal antibody used recognises red cell membrane acetylcholinesterase and the stored amniotic fluids had been frozen and thawed a number of times, the extent of this problem needs to be further assessed using freshly collected samples. The performance of this assay was found to be superior to the differential inhibitor colorimetric method and close to that of the electrophoretic procedure. The quantitative nature of the assay and the independence from operator technique makes it a useful adjunct to the measurement of amniotic fluid AFP in the prenatal diagnosis of neural tube defects.

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