Test Id : GALK
Galactokinase, Blood
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosis of galactokinase deficiency
Evaluation of children with unexplained bilateral congenital or juvenile onset cataracts
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
Enzymatic testing for the diagnosis of galactokinase deficiency.
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For more information see Galactosemia Testing Algorithm.
Method Name
A short description of the method used to perform the test
Enzyme Reaction followed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Galactokinase (RBC)
Galactokinase Deficiency
Galactosemia
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For more information see Galactosemia Testing Algorithm.
Specimen Type
Describes the specimen type validated for testing
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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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
Special Instructions
Library of PDFs including pertinent information and forms related to the test
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.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
2 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | 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 EDTA | Refrigerated (preferred) | 10 days | |
| Ambient | 72 hours |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosis of galactokinase deficiency
Evaluation of children with unexplained bilateral congenital or juvenile onset cataracts
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
Enzymatic testing for the diagnosis of galactokinase deficiency.
Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.
For more information see Galactosemia Testing Algorithm.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Galactokinase (GALK) deficiency is a very rare autosomal recessive disorder in the first step of galactose metabolism. Prevalence is unknown but is estimated to be approximately 1 in 50,000-1 in 100,000 live births, with a higher frequency in the Romani population. Individuals with GALK deficiency have a milder clinical presentation than that seen in patients with classic galactosemia, galactose-1-phosphate uridyltransferase deficiency. The major clinical manifestation is bilateral juvenile cataracts.
GALK deficiency is treated with a galactose-restricted diet. Early treatment may prevent or reverse the formation of cataracts.
In GALK deficiency, erythrocyte galactose-1-phosphate levels are generally normal, and plasma or urine galactose levels are generally elevated. The diagnosis is established by demonstrating deficient GALK enzyme activity in erythrocytes. Testing for GALK deficiency should be performed when there is a suspicion of galactosemia, either based upon the patient's clinical presentation or laboratory studies and GALT deficiency has been excluded. Specimens sent for GALT analysis may be used for GALK testing if the original specimen was received in the laboratory within the stability parameters listed in Specimen Stability Information.
GALK deficiency is caused by variants in the GALK1 gene. Molecular analysis of the GALK1 gene is available; order CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies and specify Gene List ID: IEMCP-C2DU1U.
For more information see Galactosemia Testing Algorithm.
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.
> or =0.7 nmol/h/mg of hemoglobin
Interpretation
Provides information to assist in interpretation of the test results
An interpretive report will be provided.
Deficient galactokinase enzyme activity in erythrocytes is diagnostic for galactokinase deficiency.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The results of testing performed in erythrocytes, including analysis of enzymes, biochemical phenotyping, or galactose-1-phosphate, are invalid following a transfusion.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Pasquali M, Yu C, Coffee B. Laboratory diagnosis of galactosemia: a technical standard and guideline of the American College of Medical Genetics and Genomics (ACMG). Genet Med. 2018;20(1):3-11. doi:10.1038/gim.2017.172
2. Hennermann JB, Schadewaldt P, Vetter B, Shin YS, Monch E, Klein J. Features and outcome of galactokinase deficiency in children diagnosed by newborn screening. J Inherit Metab Dis. 2011;34(2):399-407. doi:10.1007/s10545-010-9270-8
3. Ramani PK, Arya K. Galactokinase deficiency. In: StatPearls [Internet]. StatPearls Publishing; 2021. Updated July 31, 2023. Accessed September 12, 2024. Available at www.ncbi.nlm.nih.gov/books/NBK560683/
4. Walter JH, Fridovich-Keil JL. Galactosemia. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019 Accessed September 12, 2024. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709§ionid=%20225081023
Method Description
Describes how the test is performed and provides a method-specific reference
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).
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
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
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.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
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 account representative. 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. It 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.
CPT codes are provided by the performing laboratory.
82759
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| GALK | Galactokinase, B | 81143-0 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 38005 | Galactokinase, B | 81143-0 |
| 38007 | Interpretation (GALK) | 59462-2 |
| 38006 | Reviewed By | 18771-6 |