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Test Code GAL1P Galactose-1-Phosphate, Erythrocytes

Important Note

  • Collect in Green Tube - No Gel
  • DO NOT SPIN - Send Whole Blood

Reporting Name

Galactose-1-Phosphate, RBC

Useful For

Monitoring dietary therapy of patients with galactosemia due to deficiency of galactose-1-phosphate uridyltransferase or uridine diphosphate galactose-4-epimerase

Testing Algorithm

For more information see Galactosemia Testing Algorithm.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Whole Blood EDTA


Ordering Guidance


This test is used to monitor dietary therapy of patients with galactosemia due to deficiency of galactose-1-phosphate uridyltransferase or uridine diphosphate galactose-4-epimerase.

 

This test is not appropriate for the diagnosis of galactosemia. 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 test is not appropriate for the diagnosis of epimerase deficiency, the preferred test to evaluate this deficiency is GALE / Uridine Diphosphate-Galactose 4' Epimerase, Blood.

 

If GAL1P / Galactose-1-Phosphate, Erythrocytes testing is needed, the test can be added to existing specimens if they were received in the testing laboratory within 72 hours of collection.



Necessary Information


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.

 

Patient Preparation: Specimens collected following a meal can exhibit postprandial elevations. For infants, collect a specimen immediately prior to feeding to avoid this.

Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Green top (sodium heparin)

Specimen Volume: 3 mL


Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Refrigerated 72 hours

Reference Values

Reference interval (normal range): ≤0.9 mg/dL

Therapeutic range: ≤4.9 mg/dL

Day(s) Performed

Thursday

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

84378

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GAL1P Galactose-1-Phosphate, RBC 2312-7

 

Result ID Test Result Name Result LOINC Value
24101 Galactose-1-Phosphate, RBC 2312-7

Interpretation

The concentration of galactose-1-phosphate (Gal1P) is provided along with reference values for patients with galactosemia and normal controls. The recommended Gal1P goal for patients with galactosemia is 4.9 mg/dL or less.

Clinical Reference

1. Wada Y, Kikuchi A, Arai-Ichinoi N, et al. Biallelic GALM pathogenic variants cause a novel type of galactosemia. Genet Med. 2019;21(6):1286-1294. doi:10.1038/s41436-018-0340-x

2. Iwasawa S, Kikuchi A, Wada Y, et al. The prevalence of GALM mutations that cause galactosemia: A database of functionally evaluated variants. Mol Genet Metab. 2019;126(4):362-367. doi:10.1016/j.ymgme.2019.01.018

3. 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/

4. 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 July 26, 2024. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=%20225081023

5. Timson DJ. Type IV galactosemia. Genet Med. 2019;21(6):1283-1285. doi:10.1038/s41436-018-0359-z

6. Fridovich-Keil J, Bean L, He M, et al. Epimerase deficiency galactosemia. In: Adam MP, Feldman J, Mirzaa GM, et al. eds. GeneReviews [Internet]. University of Washington, Seattle; 1993-2024. Updated March 4, 2021. Accessed September 12, 2024. Available at www.ncbi.nlm.nih.gov/books/NBK51671/

Report Available

4 to 10 days

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Forms

1. Biochemical Genetics Patient Information (T602) is recommended.

2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.