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HelpTest Code GALT 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
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
Test Classification
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
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 |
Interpretation
Results below 24.5 nmol/h/mg of hemoglobin in properly submitted specimens have different causes from carrier status for a disease-causing variant in the GALT gene (typically reduced galactose-1-phosphate uridyltransferase [GALT] activity close to the normal activity range) to "Classic Galactosemia" due to biallelic disease-causing variants in the GALT gene that abolish GALT activity. Further differentiation requires additional biochemical and molecular genetic analyses as well as correlation with clinical signs and symptoms.
Normal results (≥24.5 nmol/hour/mg of hemoglobin) are not consistent with galactosemia due to GALT deficiency.
For more information see Galactosemia Testing Algorithm.
Clinical Reference
1. Berry GT. Classic galactosemia and clinical variant galactosemia. In: Adam MP, Feldman J, Mirzaa GM, et al. eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated March 11, 2021. Accessed September 12, 2024. 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 12, 2024. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709§ionid=%20225081023
3. Carlock G, Fischer ST, Lynch ME, et al. Developmental outcomes in Duarte galactosemia. Pediatrics. 2019;143(1):e20182516. doi:10.1542/peds.2018-2516
4. Anderson S. GALT deficiency galactosemia. MCN Am J Matern Child Nurs. 2018;43(1):44-51. doi:10.1097/NMC.0000000000000388
Report Available
4 to 7 daysMethod 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.