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Test Code GAL1P Galactose-1-Phosphate Uridyltransferase, Blood

Reporting Name

Gal-1-P Uridyltransferase, RBC

Useful For

Diagnosis of galactose-1-phosphate uridyltransferase deficiency, the most common cause of galactosemia

 

Confirmation of abnormal state newborn screening results

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood EDTA


Ordering Guidance


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

 

This test is for galactose-1-phosphate uridyltransferase (GALT) enzyme testing only. 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.

 

This assay will not detect galactokinase (GALK) deficiency or uridine diphosphate-galactose 4' epimerase (GALE) deficiency.

-To evaluate for GALK deficiency, order GALK / Galactokinase, Blood.

-To evaluate for GALE deficiency, order GALE / Uridine Diphosphate -Galactose 4' Epimerase, Blood.

 



Necessary Information


Patient's age is required.

  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 heparin) or yellow top (ACD)

Specimen Volume: 5 mL


Specimen Minimum Volume

2 mL

Testing Algorithm

For more information see Galactosemia Testing Algorithm.

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Refrigerated (preferred) 28 days
  Ambient  14 days

Reference Values

≥24.5 nmol/h/mg of hemoglobin

Day(s) Performed

Monday, Wednesday, Friday

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 US Food and Drug Administration.

CPT Code Information

82775

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GALT Gal-1-P Uridyltransferase, RBC 24082-0

 

Result ID Test Result Name Result LOINC Value
8333 Gal-1-P Uridyltransferase, RBC 24082-0
2296 Interpretation (GALT) 59462-2
58115 Reviewed By 18771-6

Clinical Reference

1. Berry GT: Classic galactosemia and clinical variant galactosemia. In: Pagon RA, Adam MP, Ardinger HH, et al. eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated March 11, 2021. Accessed September 1, 2022. Available at www.ncbi.nlm.nih.gov/books/NBK1518/

2. 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 1, 2022. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=%20225081023

3. Carlock G, Fischer ST, Lynch ME, et al: Developmental outcomes in Duarte galactosemia. Pediatrics. 2019 Jan;143(1):e20182516. doi: 10.1542/peds.2018-2516

4. Anderson S: GALT deficiency galactosemia. MCN Am J Matern Child Nurs. 2018 Jan/Feb;43(1):44-51. doi: 10.1097/NMC.0000000000000388

Method Description

An aqueous mixture containing water, uridine diphosphate (UDP)-glucose, (13)C2-labeled galactose-1-phosphate, and UDP-N-acetylglucosamine (internal standard) is added to a hemolysate aliquot. The mixture is then vortexed briefly and incubated at 37° C for 15 minutes.

 

After incubation the reaction is quenched, extracted, and centrifuged. The top layer is then transferred to a 96-well plate. Then injected onto a liquid chromatography-tandem mass spectrometry (LC-MS/MS). The ratio of the extracted peak area of (13)C2-labeled UDP-galactose to its internal standard UDP-N-acetylglucosamine as determined by LC-MS/MS is used to calculate the concentration of product analyte in the sample. The concentration of the product is then normalized using the calculated hemoglobin concentration to determine the patient's enzyme level in nmol/h/mg of hemoglobin.(Unpublished Mayo method)

Report Available

3 to 6 days

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.

Secondary ID

8333