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Order Code LABGOR, GALK Galactokinase, Blood

Additional Codes

Mayo Test Code: GALK

Reporting Name

Galactokinase, B

Useful For

Diagnosis of galactokinase deficiency

 

Evaluation of children with unexplained bilateral congenital or juvenile onset cataracts

Testing Algorithm

For more information see Galactosemia Testing Algorithm.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood EDTA


Ordering Guidance


This test is for diagnosis of galactokinase (GALK) deficiency and does not detect either galactose-1-phosphate uridyltransferase (GALT) deficiency (the most common cause of galactosemia), uridine diphosphate-galactose 4' epimerase (GALE) deficiency, or galactose mutarotase (GALM) deficiency. In most cases, GALT deficiency should be ruled out prior to evaluating for GALK deficiency.

-The preferred test to evaluate for possible diagnosis of galactosemia, routine carrier screening, and follow-up of abnormal newborn screening results is GCT / Galactosemia Reflex, Blood.

-To evaluate GALT deficiency only, order GALT / Galactose-1-Phosphate Uridyltransferase, Blood

-To evaluate for GALE deficiency only, order GALE / UDP-Galactose 4' Epimerase (GALE), Blood

-To evaluate for GALM deficiency, order GALP / Galactose, Plasma and molecular analysis of the GALM gene.

 

This assay is not appropriate for monitoring dietary compliance. If dietary monitoring is needed, order GAL1P / Galactose-1-Phosphate, Erythrocytes.



Necessary Information


Biochemical Genetics Patient Information (T602) is recommended, but not required, to be filled out and sent with the specimen to aid in the interpretation of test results.



Specimen Required


Multiple whole blood tests for galactosemia can be performed on 1 specimen. Prioritize order of testing when submitting specimens. For a list of tests that can be ordered together see Galactosemia-Related Test List.

 

Container/Tube:

Preferred: Lavender top (EDTA)

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

Specimen Volume: 4 mL


Specimen Minimum Volume

2 mL

Specimen Stability Information

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

Reference Values

≥0.7 nmol/h/mg of hemoglobin

Day(s) Performed

Monday

CPT Code Information

82759

Method Description

A buffered enzyme incubation with substrate and cofactors is performed on lysed red blood cells. A post-incubation extraction is performed and subjected to liquid chromatography tandem mass spectrometry. The ratio of the extracted product to its internal standard is used to calculate the total enzymatic product. This is then normalized using the calculated hemoglobin concentration to determine the patient's enzyme level in nmol/h/mg of hemoglobin.(Unpublished Mayo method).

Reject Due To

Gross hemolysis Reject

Method Name

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

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:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) is recommended.

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Genetics Test Information

Enzymatic testing for the diagnosis of galactokinase deficiency.