Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

FUCT
8815
Useful For: Screening for open neural tube defects or other fetal abnormalities Follow-up testing for
patients with elevated serum alpha-fetoprotein results or in conjunction with cytogenetic testing
Interpretation: A diagnostic alpha-fetoprotein (AFP) cutoff level of 2.0 multiples of median (MoM),
followed by acetylcholinesterase (AChE) confirmatory testing on positive results, is capable of detecting
96% of open spina bifida cases with a false-positive rate of only 0.06% in non blood-stained specimens.
AChE analysis is an essential confirmatory test for all amniotic fluid specimens with positive AFP results.
Normal amniotic fluid does not contain AChE, unless contributed by the fetus as a result of open
communication between fetal central nervous system (eg, open neural tube defects), or to a lesser degree,
fetal circulation. All amniotic fluid specimens testing positive for AFP will have the AChE test
performed. Because false-positive AChE may occur from a bloody tap, specimens with positive AChE
results will also be tested for the presence of fetal hemoglobin, which may cause both elevated AFP and
AChE levels.
Reference Values:
< or =2.0 multiples of median (MoM)
Clinical References: Assessing the Quality of Systems for Alpha-Fetoprotein (AFP) Assays Used in
Prenatal Screening and Diagnosis of Open Neural Tube Defects: Approved Guideline. NCCLS I/LA17-A
Vol 17. No 5. April 1997
Alpha-Fucosidase, Fibroblasts
Clinical Information: Fucosidosis is an autosomal recessive lysosomal storage disorder caused by
reduced or absent alpha-L-fucosidase enzyme activity. This enzyme is involved in degrading
asparagine-linked, fucose-containing complex molecules (oligosaccharides, glycoasparagines) present in
cells. Reduced or absent activity of this enzyme results in the abnormal accumulation of these undigested
molecules in the tissues and body fluids of fucosidosis patients. Although the disorder is pan ethnic, the
majority of reported patients have been from Italy and southwestern United States. To date, less than 80
patients have been reported in the literature. Severe and mild subgroups of fucosidosis, designated types I
and II, have been described, although recent data suggests individual patients may represent a continuum
within a wide spectrum of severity. The more severe type is characterized by infantile onset, rapid
psychomotor regression and severe neurologic deterioration. Additionally, dysostosis multiplex and
elevated sweat sodium chloride are frequent findings. Death typically occurs within the first decade of
life. Those with the milder phenotype express comparatively mild psychomotor and neurologic
regression, radiologic signs of dysostosis multiplex, and skin lesions (angiokeratoma corporis diffusum).
Normal sweat salinity, the presence of the skin lesions, and survival into adulthood most readily
distinguish milder from more severe phenotypes. A diagnostic work-up includes urine thin-layer
chromatography (OLIGO/84340 Oligosaccharide Screen, Urine) which may reveal the characteristic
banding pattern associated with fucosidosis. In addition, enzyme assay of alpha-L-fucosidosis can confirm
the diagnosis. Enzyme analysis should be pursued in cases with strong clinical suspicion regardless of the
urine screening result. Molecular (DNA) analysis is not currently available in the US.
Useful For: Detection of fucosidosis
Interpretation: Low alpha-fucosidase suggests fucosidosis when accompanied with clinical findings.
Some patients exhibit measurable activity minimally below the normal range. These patients are not likely
to have fucosidosis.
Reference Values:
1.30-3.60 U/g of cellular protein
Clinical References: 1. Cowan TM, Yu C: Laboratory investigations of inborn errors of metabolism.
In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS
Roth, New York, NY,McGraw-Hill Medical Division, 2009, pp 867-868 2. Enns GM, Steiner RD, Cowan
TM: Lysosomal disorders. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K
Sarafoglou, GF Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 747-748 3.
Thomas GH: Disorders of glycoprotein degradation: alpha-mannosidosis, beta-mannosidosis, fucosidosis,
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