Test Code GALACCB Galactocerebrosidase, Leukocytes
Advisory Information
This test will not detect carrier status. For differentiating alterations from disease-causing variants in affected patients and for carrier detection in family members, molecular sequencing of the GALC gene is necessary. Order KRABZ / Krabbe Disease, Full Gene Analysis and Large (30 kb) Deletion, PCR, Varies.
Shipping Instructions
For optimal isolation of leukocytes, it is recommended the specimen arrive refrigerate within 96 hours of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.
Specimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A) or lavender top (EDTA)
Specimen Volume: 6 mL
Collection Instructions: Send specimen in original tube. Do not transfer blood to other containers.
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2.Biochemical Genetics Patient Information (T602) in Special Instructions
Useful For
Diagnosis of Krabbe disease
Follow-up testing for evaluation of an abnormal newborn screening result for Krabbe disease
This test is not intended for carrier detection.
Testing Algorithm
The following are available in Special Instructions:
-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase
-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase and Psychosine
-Newborn Screening Act Sheet Krabbe Disease: Decreased Galactocerebrosidase
Special Instructions
- Informed Consent for Genetic Testing
- Biochemical Genetics Patient Information
- Newborn Screening Act Sheet Krabbe Disease: Decreased Galactocerebrosidase
- Informed Consent for Genetic Testing (Spanish)
- Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase
- Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase and Psychosine
- Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase, Psychosine, and GALC 30kb Deletion
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Galactocerebrosidase, WBCSpecimen Type
Whole Blood ACDSpecimen Minimum Volume
2 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Whole Blood ACD | Refrigerated (preferred) | 4 days | |
Ambient | 72 hours |
Reject Due To
Gross hemolysis | Reject |
Clinical Information
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 causing 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 found. 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 age 2. 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 some 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.
Reduced or absent galactocerebrosidase in leukocytes 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 in vitro, but do not 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, PCR, Varies) is necessary for differentiating alterations from disease-causing variants in affected patients and for carrier detection in family members.
Reference Values
≥0.30 nmol/hour/mg protein
An interpretative report will be provided.
Day(s) and Time(s) Performed
Specimens are processed Monday through Sunday.
Assay is performed: Varies
Analytic Time
5 daysPerforming Laboratory

Test Classification
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 U.S. Food and Drug Administration.CPT Code Information
82657
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
GALCW | Galactocerebrosidase, WBC | 24084-6 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
606270 | Galactocerebrosidase, WBC | 24084-6 |
606271 | Interpretation | 59462-2 |
606272 | Reviewed By | 18771-6 |
NY State Approved
YesComputer Interface Code
PDM # 5902430