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Epic Test Code GPSYW Glucopsychosine, Blood


Specimen Required


Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Sodium heparin, lithium heparin, ACD B

Specimen Volume: 1 mL


Forms

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

2. Biochemical Genetics Patient Information (T602) in Special Instructions.

Useful For

Second-tier test when newborn screens with reduced GBA (beta-glucosidase) activity are identified

 

Diagnosis and monitoring of patients with Gaucher disease

 

Documentation of an elevated glucopsychosine (glucosylsphingosine) level supports the biochemical diagnosis of Gaucher disease

 

May aid in monitoring a patient's response to treatment

Highlights

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by deficient beta-glucosidase activity.

 

There are 3 described types of Gaucher disease with varying clinical presentations and age of onset from a perinatal lethal disorder to an asymptomatic type.

 

Glucopsychosine is elevated in symptomatic patients and supports a diagnosis of Gaucher disease.

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Glucopsychosine, B

Specimen Type

Whole blood

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Refrigerated (preferred) 72 hours
  Ambient  48 hours

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

Clinical Information

Gaucher disease is an autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme, beta-glucosidase. 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 presentations and age of onset from a perinatal lethal disorder to an asymptomatic type. Features of all types 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. Gaucher disease types II and III are characterized by the presence of primary neurologic disease. In addition, Type II typically presents with limited psychomotor development, 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. Additional subtypes 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, corneal opacities, and gaze impairment.

 

Treatment is available in the form of enzyme replacement therapy and 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), or dried blood spots (PLSD / Lysosomal and Peroxisomal Storage Disorders Screen, Blood Spot) and molecular genetic analysis of the GBA gene (GAUP / Gaucher Disease, Mutation Analysis, GBA; or GBAZ / Gaucher Disease, Full Gene Analysis). Glucopsychosine is elevated in symptomatic patients and supports a diagnosis of Gaucher disease. It may also be helpful in determining treatment response.

Reference Values

GLUCOPSYCHOSINE (GPSY)

Cutoff: ≤0.040 nmol/mL

Interpretation

An elevation of glucopsychosine is indicative of Gaucher disease.

Cautions

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

Day(s) and Time(s) Performed

Tuesday and Thursday 8 a.m.

 

Analytic Time

2 days

Specimen Retention Time

Whole blood: 7 days Dried Blood Spot: Normals: 1 year; Abnormal: Indefinitely

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82542

NY State Approved

Yes