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Test ID GALK Galactokinase, Blood

Useful For

Diagnosis of galactokinase deficiency, the second most common cause of galactosemia

Highlights

Galactokinase (GALK) deficiency is a milder form of galactosemia that results in cataracts, which are preventable with a lactose-restricted diet.

 

Deficient GALK enzyme activity in erythrocytes is diagnostic for galactokinase deficiency.

 

In GALK deficiency, erythrocyte galactose-1-phosphate levels are normal, whereas plasma galactose levels are elevated.

 

The results of testing performed in erythrocytes are invalid following a transfusion, including analysis of enzymes, biochemical phenotyping, or galactose-1-phosphate.

Method Name

Enzyme Reaction Followed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Galactokinase, B

Specimen Type

Whole Blood EDTA


Advisory Information


This test is for diagnosis of galactokinase (GALK) deficiency. The most common cause of galactosemia is GALT deficiency. In most cases, GALT deficiency should be ruled out prior to evaluating for galactokinase (GALK) deficiency (see GCT / Galactosemia Reflex, Blood).

 

To evaluate for galactose-1-phosphate uridyltransferase deficiency, see GALT / Galactose-1-Phosphate Uridyltransferase, Blood.

 

This assay will not detect UDP-galactose 4' epimerase (GALE) deficiency or galactose-1-phosphate uridyltransferase (GALT) deficiency. For epimerase deficiency, see GALE / UDP-Galactose 4' Epimerase (GALE), Blood.

 

This assay is not appropriate for monitoring dietary compliance; see GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes.



Specimen Required


Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Green top (sodium heparin), green top (lithium heparin), or yellow top (ACD)

Specimen Volume: 4 mL


Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood EDTA Refrigerated (preferred) 10 days
  Ambient  72 hours

Reference Values

≥0.7 nmol/h/mg of hemoglobin

Day(s) and Time(s) Performed

Mondays; 9 a.m.

Performing Laboratory

Mayo Medical Laboratories in Rochester

CPT Code Information

82759

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GALK Galactokinase, B 81143-0

 

Result ID Test Result Name Result LOINC Value
38005 Galactokinase, B In Process
38007 Interpretation (GALK) In Process
38006 Reviewed By No LOINC Needed

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.

Testing Algorithm

See Galactosemia Testing Algorithm in Special Instructions.

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.