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Test ID: GPSY    
Glucopsychosine, Blood Spot

Useful For Suggests clinical disorders or settings where the test may be helpful

Quantification of glucopsychosine (glucosylsphingosine) in dried blood spots supports the biochemical diagnosis of Gaucher disease

 

May aid in monitoring a patient’s response to treatment

Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request

This test is used as a second-tier newborn screen and to diagnose and monitor patients with Gaucher disease.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by a deficiency of beta-glucosidase activity. Beta-glucosidase facilitates the lysosomal degradation of glucosylceramide (glucocerebroside) and glucopsychosine (glucosylsphingosine). Gaucher disease is caused by mutations in the GBA gene. There are 3 described types of Gaucher disease with varying clinical presentation and age of onset. Features of all variants of Gaucher disease include hepatosplenomegaly and hematological abnormalities.

 

Gaucher disease type I is the most common, representing more than 90% of cases. It is generally characterized by bone disease, hepatosplenomegaly, anemia and thrombocytopenia, coagulation abnormalities, lung disease, but no central nervous system (CNS) involvement. Type II (acute neuronopathic Gaucher disease) typically presents with neurologic disease, hepatosplenomegaly, and lung disease, resulting in death usually between 2 and 4 years of age. Individuals with Gaucher disease type III may present prior to 2 years of age, but the progression is not as rapid and patients may survive into the third and fourth decade. Further variants of Gaucher disease include a perinatal lethal form associated with skin abnormalities and nonimmune hydrops fetalis, and a cardiovascular form presenting with calcification of the aortic and mitral valves, mild splenomegaly, and corneal opacities.

 

Treatment is available in the form of enzyme replacement therapy and/or substrate reduction therapy for types I and III. These treatment options have generally made bone marrow transplantation obsolete. Currently, only supportive therapy is available for type II because of the inability of enzyme provided by replacement therapy to cross the blood-brain barrier.

 

The incidence of Gaucher disease type I ranges from 1 in 30,000 to 1 in 100,000 in the general population, but is much more frequent among Ashkenazi Jews with an incidence of approximately 1 in 900. Types II and III both have an incidence of approximately 1 in 100,000 in the general population.

 

A diagnostic workup for Gaucher disease may demonstrate the characteristic finding of Gaucher cells on bone marrow examination, other hematologic abnormalities, and hepatosplenomegaly. The diagnosis can be confirmed by the demonstration of reduced or absent acid beta-glucosidase activity in leukocytes (BGL / Beta-glucosidase, Leukocytes) and molecular genetic analysis of the GBA gene (GAUW / Gaucher Disease, Mutation Analysis, GBA; or GBAMS / Gaucher Disease, Full Gene Analysis, GBA). Glucopsychosine is elevated in symptomatic patients and may be helpful in determining treatment response.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Normal <47 nmol/L glucopsychosine

Interpretation Provides information to assist in interpretation of the test results

An elevation of glucopsychosine is indicative of Gaucher disease.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is not capable of identifying carriers of GBA mutations.

Supportive Data

ROC analysis of 220 controls and 25 patients affected with Gaucher disease yielded an area under the curve of 1.0, permitting the selection of a cutoff value yielding a positive predictive value and negative predictive value of 1.0.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Orvisky E, Park J, LaMarca M, et al: Glucosylsphingosine accumulation in tissues from patients with Gaucher disease: correlation with phenotype and genotype. Mol Genet Metab 2002;76:262-270

2. Schueler U, Kolter T, Kaneski C, et al: Toxicity of glucosylsphingosine (glucopsychosine) to cultured neuronal cells: a model system for assessing neuronal damage in Gaucher disease type 2 and 3. Neurobiol Dis 2003;14:595-601

3. Dekker N, Dussen L, Hollak C, et al: Elevated plasma glucosylsphingosine in Gaucher disease: relation to phenotype, storage cell markers, and therapeutic response. Blood 2011;118(16):118-127

4. Kaplan P, Baris H, De Meirleir L, et al: Revised recommendations for the management of Gaucher disease in children. Eur J Pediatr 2013;172:447-58

5. Grabowski GA, Petsko GA, Kolodny EH: Gaucher Disease. In The Online Metabolic and Molecular Bases of Inherited Diseases. Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York: McGraw-Hill; 2013, http://ommbid.mhmedical.com/content.aspx?bookid=474&Sectionid=45374148. Accessed January 21, 2014.

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test