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HelpTest Code GAL1P Galactose-1-Phosphate Uridyltransferase, Blood
Reporting Name
Gal-1-P Uridyltransferase, RBCUseful 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 EDTAAdvisory Information
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 followup 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 / UDP-Galactose 4' Epimerase, Blood.
This assay is not appropriate for monitoring dietary compliance. If dietary monitoring is needed, order GAL1P / Galactose-1-Phosphate, Erythrocytes.
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. See Galactosemia-Related Test List in Special Instructions for a list of tests that can be ordered together.
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
See Galactosemia Testing Algorithm in Special Instructions.
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood EDTA | Refrigerated (preferred) | 28 days | |
| Ambient | 14 days |
Special Instructions
Reference Values
≥24.5 nmol/h/mg of hemoglobin
Day(s) and Time(s) Performed
Monday, Wednesday, Friday; 7 a.m. (specimen must be received the day prior)
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
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 GeneReviews. Edited by MP Adam, HH Ardinger, RA Pagon, et al. University of Washington, Seattle Updated 2017 Mar 9 Accessed: February 20, 2020 Available at https://www.ncbi.nlm.nih.gov/books/NBK1518/
2. Walter JH, Fridovich-Keil JL: Galactosemia. In The Online Metabolic and Molecular Bases of Inherited Disease. Edited by D Valle, AL Beaudet, B Vogelstein, et al. McGraw-Hill. Accessed June 18, 2019. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971§ionid=62672411
3. Carlock G, Fischer ST, Lynch ME, et al. Developmental Outcomes in Duarte Galactosemia. Pediatrics. 2018;143(1):e20182516. doi:10.1542/peds.2018-2516
Method Description
An aqueous mixture containing CLR H2O, 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 (Nunc, polypropylene) plate. Then injected onto a liquid chromatography-tandem mass spectrometry (LC-MS/MS) The ratio of the extracted peak area of (13)C2labeled 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)
Analytic Time
4 days (not reported on Saturday or Sunday)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 in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Biochemical Genetics Patient Information (T602) is recommended, see Special Instructions.
3. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.