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HelpOrder Code LABGCT Galactose-1-Phosphate Uridyltransferase, Blood
Additional Codes
Mayo Test Code: GALT
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
Testing Algorithm
For more information see Galactosemia Testing Algorithm.
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Whole Blood EDTAOrdering 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.
-To evaluate for GALM deficiency, order GALP / Galactose, Plasma and molecular analysis of the GALM gene.
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
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) Performed
Monday, Wednesday, Friday
CPT Code Information
82775
Genetics Test Information
Galactose-1-phosphate uridyltransferase (GALT) deficiency is the most common cause of galactosemia and requires lifelong restriction of dietary galactose.
Classic galactosemia can be diagnosed by analysis of GALT enzyme.
This test provides enzymatic testing for the diagnosis of GALT deficiency.
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)
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.