Galactose-1-Phosphate Uridyltransferase, Blood

Reporting Name

Gal-1-P Uridyltransferase, RBC

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

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

Confirmation of abnormal state newborn screening results

Method Name

Enzyme Reaction followed by Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

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.

-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 Type

Whole Blood EDTA

Specimen Minimum Volume

2 mL

Specimen Stability Information

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

Reject Due To

Gross hemolysis

Reject

Reference Values

≥24.5 nmol/h/mg of hemoglobin

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.

Day(s) Performed

Monday, Wednesday, Friday

Report Available

4 to 7 days

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

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.

Testing Algorithm