Test Catalog

Test Id : GALCB

Galactocerebrosidase, Blood Spot

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

Evaluation of patients with a clinical presentation suggestive of Krabbe disease

 

Longitudinal evaluation of treatment following hematopoietic stem cell transplantation and gene therapy.

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

This test provides diagnostic testing for patients with clinical signs and symptoms suspicious for Krabbe disease.

 

Enzyme testing for galactocerebrosidase is included in the diagnostic workup for infants following a positive newborn screen result for Krabbe disease.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

No

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Galactocerebrosidase, BS

Aliases
Lists additional common names for a test, as an aid in searching

Galactocerebrosidase

Galactosylceramidase

GALC

Krabbe Disease

Specimen Type
Describes the specimen type validated for testing

Whole blood

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Card-Blood Spot Collection (Filter Paper)

Acceptable: PerkinElmer 226 (formerly Ahlstrom 226) filter paper, Munktell filter paper, Whatman Protein Saver 903 paper, or blood collected in tubes containing ACD, EDTA, or heparin and dried on acceptable filter paper

Specimen Volume: 2 blood spots

Collection Instructions:

1. An alternative blood collection option for a patient older than 1 year of age is fingerstick. See Dried Blood Spot Collection Tutorial for how to collect blood spots via fingerstick: https://vimeo.com/508490782 .

2. Completely fill at least 2 circles on the filter paper card (approximately 100 microliters blood per circle).

3. Let blood dry on the filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.

4. Do not expose specimen to heat or direct sunlight.

5. Do not stack wet specimens.

6. Keep specimen dry.

Additional Information:

1. For collection instructions, see Blood Spot Collection Instructions in Special Instructions.

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777) in Special Instructions.

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800) in Special Instructions.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

Biochemical Genetics Patient Information (T602) in Special Instructions

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1 Blood spot

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Shows serum rings
Insufficient specimen
Layering
Multiple applications
Incubated/exposed to temperatures above 37 degrees C
Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 56 days FILTER PAPER
Frozen 56 days FILTER PAPER
Ambient 7 days FILTER PAPER

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

Evaluation of patients with a clinical presentation suggestive of Krabbe disease

 

Longitudinal evaluation of treatment following hematopoietic stem cell transplantation and gene therapy.

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

This test provides diagnostic testing for patients with clinical signs and symptoms suspicious for Krabbe disease.

 

Enzyme testing for galactocerebrosidase is included in the diagnostic workup for infants following a positive newborn screen result for Krabbe disease.

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

Krabbe disease (globoid cell leukodystrophy) is an autosomal recessive disorder caused by a deficiency of the enzyme, galactocerebrosidase (GALC). GALC facilitates the lysosomal degradation of psychosine (galactosylsphingosine) and 3 other substrates (galactosylceramide, lactosylceramide and lactosylsphingosine), which can cause severe demyelination throughout the brain. Krabbe disease is caused by variants in the GALC gene, and it has an estimated frequency of 1 in 100,000 births. Although rare, a few infants with an early onset Krabbe disease phenotype due to deficiency of saposin A have been reported. Saposin A is a sphingolipid activator protein that assists galactocerebrosidase in its action on galactosylceramide.

 

Severely affected individuals typically present between 3 to 6 months of age with increasing irritability and sensitivity to stimuli. Rapid neurodegeneration including white matter disease follows with death usually occurring by two years old. Some individuals have later onset forms of the disease that are characterized by ataxia, vision loss, weakness, and psychomotor regression presenting anywhere from age 6 months to the seventh decade of life. The clinical course of Krabbe disease can be variable, even within the same family.

 

Newborn screening for Krabbe disease has been implemented in several states. The early (presymptomatic) identification and subsequent testing of infants at risk for Krabbe disease may be helpful in reducing the morbidity and mortality associated with this disease. While treatment is mostly supportive, hematopoietic stem cell transplantation has shown some success if performed prior to onset of neurologic damage. Moreover, in the spring of 2021, the first gene therapy trial was initiated, which may allow for improved outcomes for patients identified before showing clinical symptoms (clinicaltrials.gov).

 

Reduced or absent galactocerebrosidase activity can indicate a diagnosis of Krabbe disease, however a number of alterations in the GALC gene have been identified that result in reduced galactocerebrosidase activity but not to a level to cause disease. The biomarker, psychosine (see PSY / Psychosine, Blood Spot), has been shown to be elevated in patients with active Krabbe disease. Molecular sequencing of the GALC gene (see KRABZ / Krabbe Disease, Full Gene Analysis and Large [30 kb] Deletion, Varies) is necessary for differentiating alterations from disease-causing variants in affected patients and for carrier detection in family members.

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.

Galactocerebrosidase

> or =0.4 nmol/mL/hr

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be provided.

 

When abnormal results are detected, a detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing, and in vitro confirmatory studies (enzyme assay, molecular analysis), and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

 

Abnormal results are not sufficient to conclusively establish a diagnosis of a particular disease. To verify a preliminary diagnosis based on the analysis, independent biochemical (eg, biomarker such as psychosine) or molecular genetic analysis is required.

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

Pseudodeficiency of galactocerebrosidase causes reduced enzymatic activity but does not cause disease.

 

A Krabbe disease phenotype can also be caused in very rare cases by the absence of a physiologically active sphingolipid activator protein, saposin A.

 

GALC activity may be normal in individuals who have undergone hematopoietic stem cell transplant or received gene therapy.

 

Carrier status (heterozygosity) for these conditions cannot be reliably detected.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Minter-Baerg M, Stoway SD, Hart J, et al: Precision newborn screening for lysosomal disorders. Genet Med. 2018;20:847-854

2. Guenzel AJ, Turgeon CT, Nickander KK, et al: The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease. Genet Med. 2020;22:1108-1118

3. Orsini JJ, Escolar ML, Wasserstein MP, Caggana M: Krabbe disease. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated October 11, 2018. Accessed June 29, 2021. Available at www.ncbi.nlm.nih.gov/books/NBK1238/

4. Kwon JM, Matern DM, Kurtzberg J, et al: Consensus guidelines for newborn screening, diagnosis, and treatment of infantile Krabbe disease. Orphanet J Rare Dis. 2018;13:30. doi: 10.1186/s13023-018-0766

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

Dried blood spots (DBS) are excised from a single specimen. The enzyme is extracted by incubating the sample with a mix of substrate and internal standard for galactocerebrosidase. The sample is then purified by liquid-liquid extraction. and subjected to analysis by tandem mass spectrometry.(Tortorelli S, Turgeon CT, Gavrilov DK, et al: Simultaneous testing for 6 lysosomal storage disorders and X-adrenoleukodystrophy in dried blood spots by tandem mass spectrometry. Clin Chem. 2016;62:1248-1254)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 8 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

6 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

83789

LOINC® Information

Test Id Test Order Name Order LOINC Value
GALCB Galactocerebrosidase, BS 62310-8
Result Id Test Result Name Result LOINC Value
Result LOINC Value Tooltip
614799 Interpretation 59462-2
614798 Galactocerebrosidase 62310-8
614800 Reviewed By 18771-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports