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HelpTest Code GCT Galactosemia Reflex, Blood
Reporting Name
Galactosemia Reflex, BUseful For
Preferred test for diagnosis, carrier detection, and determination of genotype of galactose-1-phosphate uridyltransferase deficiency, the most common cause of galactosemia
Differentiating Duarte variant galactosemia from classic galactosemia
Confirming results of newborn screening programs
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| GALZ | Galactosemia, Full Gene Analysis | Yes | No |
Testing Algorithm
Testing begins with galactose-1-phosphate uridyltransferase (GALT) enzyme analysis. If GALT activity is greater than or equal to 24.5 nmol/h/mg of hemoglobin, testing is complete. No molecular test will be performed. If GALT activity is less than 24.5 nmol/h/mg of hemoglobin, galactosemia full gene sequencing will be performed at an additional charge.
For more information see Galactosemia Testing Algorithm
Method Name
Enzyme Reaction followed by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Whole Blood EDTAOrdering Guidance
This test is appropriate for the diagnosis of, and routine carrier screening for, galactose-1-phosphate uridyltransferase deficiency.
This assay is not appropriate for monitoring dietary compliance. For dietary monitoring, order GAL1P / Galactose-1-Phosphate, Erythrocytes.
Necessary Information
Patient's age is required.
Specimen Required
Multiple whole blood tests for galactosemia can be performed on one 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
Collection Instructions:
1. Invert several times to mix blood.
2. Send whole blood specimen in original tube. Do not aliquot.
Specimen Minimum Volume
2 mL
Reject Due To
| Gross hemolysis | Reject |
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
81406 (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| GCT | Galactosemia Reflex, B | 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 |
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.Report Available
4 to 7 daysForms
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. If not ordering electronically, complete, print, and send an Biochemical Genetics Test Request (T798) with the specimen.