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Test ID GCT Galactosemia Reflex, Blood

Useful 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

Genetics Test Information

Preferred test to evaluate for possible diagnosis of galactosemia, routine carrier screening, and follow-up of abnormal newborn screening results. Comprehensive reflex test begins with quantitative galactose-1-phosphate uridyltransferase (GALT) enzyme analysis. If quantitative GALT enzyme value is consistent with a diagnosis of or carrier status for galactosemia, DNA analysis of the GALT gene is performed to detect 14 galactosemia alleles: -119_-116delGTCA, D98N, S135L, T138M, M142K, F171S, Q188R, L195P, Y209C, K285N, N314D, Q344K, c.253-2A>G, and 5 kb deletion.

Method Name

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

Reporting Name

Galactosemia Reflex, B

Specimen Type

Whole Blood EDTA


Ordering Guidance


This test is appropriate for the diagnosis of and routine carrier screening for galactose-1-phosphate uridyltransferase (GALT) deficiency.

 

This assay is not appropriate for monitoring dietary compliance. For dietary monitoring, order GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes.

Necessary Information


Patient's age is required.



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: 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

Reference Values

≥24.5 nmol/h/mg of hemoglobin

Day(s) Performed

Monday, Wednesday, Friday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82775

 

81401-GALT (galactose-1-phosphate uridylyltransferase) (eg, galactosemia), common variants (eg, Q188R, S135L, K285N, T138M, L195P, Y209C, IVS2-2A->G, P171S, del5kb, N314D, L218L/N314D, 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. This test has not been cleared or approved by the US Food and Drug Administration.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
GAL14 Galactosemia Gene Analysis Yes No

Testing Algorithm

Testing begins with galactose-1-phosphate uridyltransferase (GALT) enzyme analysis. If GALT is greater than or equal to 24.5 nmol/h/mg of hemoglobin, testing is complete. No molecular test will be performed. If GALT is less than 24.5 nmol/h/mg of hemoglobin, galactosemia gene analysis) will be performed at an additional charge.

 

See Galactosemia Testing Algorithm in Special Instructions.

Disease States

  • Galactosemia

Report Available

4 to 5 days

NY State Approved

Yes

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. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.