Sorted By Test Name - Mayo Medical Laboratories

SFIN
8009
features are behavior problems, declining school performance, clumsiness, and slurred speech.
Neurodegeneration occurs at a somewhat slower and more variable rate than the late-infantile form. Adult
MLD (15%-20% of cases) has an onset after puberty and can be as late as the fourth or fifth decade.
Presenting features are often behavior and personality changes, including psychiatric symptoms;
clumsiness, neurologic symptoms, and seizures are also common. The disease course has variable
progression and may occur over 2 to 3 decades. Individuals with MLD typically show an increased
excretion of sulfatides in urine. Extremely low arylsulfatase A levels have been found in some clinically
normal parents and other relatives of MLD patients. These individuals do not have metachromatic
deposits in peripheral nerve tissues, and their urine content of sulfatide is normal. Individuals with this
"pseudodeficiency" have been recognized with increasing frequency among patients with other apparently
unrelated neurologic conditions as well as among the general population. This has been associated with a
fairly common polymorphism in the arylsulfatase A gene, which leads to low expression of the enzyme
(5%-20% of normal). These patients can be difficult to differentiate from actual MLD patients.
Useful For: As an aid in identifying patients with Fabry disease As an aid in identifying patients with
metachromatic leukodystrophy
Interpretation: No evidence of ceramide trihexosides or sulfatide accumulation suggests normal
enzyme activities. Evidence of ceramide trihexoside accumulation suggests decreased or deficient
alpha-galactosidase activity. Follow-up testing with the specific enzyme assay is recommended:
AGA/8785 Alpha-Galactosidase, Leukocytes; AGABS/89407 Alpha-Galactosidase, Blood Spot; and
AGAS/8784 Alpha-Galactosidase, Serum. Evidence of sulfatide accumulation suggests decreased or
deficient arylsulfatase A activity. Follow-up with the specific enzyme assay is recommended:
ARSAW/8779 Arylsulfatase A, Leukocytes, ARST/8778 Arylsulfatase A, Fibroblasts; and ARSU/8777
Arylsulfatase A, Urine. See Fabry Disease Testing Algorithm in Special Instructions.
Reference Values:
No evidence of ceramide trihexoside/sulfatide accumulation
Clinical References: 1. Eng CM, Ioannou YA, Desnick RJ: Chapter 150: Alpha-galactosidase A
deficiency: Fabry disease. In Scriver's The Online Metabolic and Molecular Basis of Inherited Disease
(OMMBID). Edited by D Valle, AL Beaudet, B Vogelstein, et al. McGraw-Hill Companies, Inc. 2. Enns
GM, Steiner RD, Cowan TM: Metachromatic leukodystrophy. In Pediatric Endocrinology and Inborn
Errors of Metabolism. Edited by K Sarafoflou, GF Hoffmann, KS Roth, et al. McGraw-Hill Companies,
2009, pp 742-743 3. De Schoenmakere G, Poppe B, Wuyts B, et al: Two-tier approach for the detection of
alpha-galactosidase A deficiency in kidney transplant recipients. Nephrol Dial Transplant
2008;23:4044-4048 4. Mehta A, Hughes DA: Fabry Disease. GeneReviews. Edited by RA Pagon, TD
Bird, CR Dolan, et al. University of Washington, Seattle. Last updated March 2011 5. Spada M,
Pagliardini S, Yasuda M, et al: High incidence of later-onset Fabry disease revealed by newborn
screening. Am J Hum Genet 2006;79:31-40 6. von Figura K, Gieselmann V, Jaeken J: Chapter 148:
Metachromatic Leukodystrophy. In Scriver's The Online Metabolic and Molecular Basis of Inherited
Disease (OMMBID). Edited by D Valle, AL Beaudet, B Vogelstein, et al. McGraw-Hill Companies, Inc.
Cerebrospinal Fluid (CSF) IgG Index
Clinical Information: Elevation of IgG levels in the cerebrospinal fluid (CSF) of patients with
inflammatory diseases of the central nervous system (multiple sclerosis [MS], neurosyphilis, acute
inflammatory polyradiculoneuropathy, subacute sclerosing panencephalitis) is due to local central nervous
system (CNS) synthesis of IgG. The 2 most commonly used diagnostic laboratory tests for MS are CSF
index and oligoclonal banding. The CSF index is the CSF IgG to CSF albumin ratio compared to the
serum IgG to serum albumin ratio. The CSF index is, therefore, an indicator of the relative amount of CSF
IgG compared to serum. Any increase in the index is a reflection of IgG production in the CNS. The IgG
synthesis rate is a mathematical manipulation of the CSF index data and can also be used as a marker for
CNS inflammatory diseases.
Useful For: As an aid in the diagnosis of multiple sclerosis
Interpretation: Cerebrospinal fluid (CSF) IgG index is positive (elevated) in approximately 80% of
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