Test Catalog

Test Id : GAL1P

Galactose-1-Phosphate, Erythrocytes

Useful For
Suggests clinical disorders or settings where the test may be helpful

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

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Galactose-1-phosphate uridyltransferase (GALT) deficiency is the most common cause of galactosemia and requires lifelong restriction of dietary galactose.

 

Galactose-1-phosphate is elevated in patients with galactosemia due to GALT deficiency or uridine diphosphate galactose-4-epimerase (GALE) deficiency, therefore is a suitable analyte for monitoring dietary compliance.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Galactosemia Testing Algorithm in Special Instructions

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

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

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Galactose-1-Phosphate, RBC

Aliases
Lists additional common names for a test, as an aid in searching

Gal1P

Galactosemia

Galactose-1-Phosphate

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Galactosemia Testing Algorithm in Special Instructions

Specimen Type
Describes the specimen type validated for testing

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 (GALT) or uridine diphosphate galactose-4-epimerase (GALE).

 

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 / UDP-Galactose 4' Epimerase, Blood.

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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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.

 

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

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

2 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

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

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Galactose-1-phosphate uridyltransferase (GALT) deficiency is the most common cause of galactosemia and requires lifelong restriction of dietary galactose.

 

Galactose-1-phosphate is elevated in patients with galactosemia due to GALT deficiency or uridine diphosphate galactose-4-epimerase (GALE) deficiency, therefore is a suitable analyte for monitoring dietary compliance.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Galactosemia Testing Algorithm in Special Instructions

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Galactosemia is an autosomal recessive disorder that results from a deficiency of any 1 of the 4 enzymes catalyzing the conversion of galactose to glucose: galactose-1-phosphate uridyltransferase (GALT), galactokinase (GALK), uridine diphosphate galactose-4-epimerase (GALE), and galactose mutarotase (GALM). Galactose-1-phosphate (Gal-1-P) accumulates in the erythrocytes of patients with galactosemia due to GALT, GALE, or neonates with GALM deficiency. The quantitative measurement of Gal-1-P is useful for monitoring compliance with dietary therapy for either GALT or GALE deficiency. Gal-1-P is thought to be the causative factor for development of liver disease in these patients and, because of this, patients should maintain low levels and be monitored on a regular basis. The concentration of Gal-1-P in erythrocytes is the most sensitive index of dietary control.

 

GALT deficiency is the most common cause of galactosemia and is often referred to as classic galactosemia. The complete or near-complete deficiency of GALT enzyme is life-threatening if left untreated. Complications in the neonatal period include failure to thrive, liver failure, sepsis, and death.

 

Galactosemia due to GALT deficiency is treated by a galactose-restricted diet, which allows for rapid recovery from the acute symptoms and a generally good prognosis. Despite adequate treatment from an early age, individuals with galactosemia remain at increased risk for developmental delays, speech problems, and abnormalities of motor function. Female patients with galactosemia are at increased risk for premature ovarian failure. Based upon reports by newborn screening programs, the frequency of classic galactosemia in the United States is approximately 1 in 30,000, although literature reports range from 1 in 10,000 to 1 in 60,000 live births.

 

Epimerase deficiency galactosemia can be categorized into 3 types: generalized, peripheral, and intermediate. Generalized epimerase deficiency galactosemia results in profoundly decreased enzyme activity in all tissues, whereas peripheral epimerase deficiency galactosemia results in decreased enzyme activity in red and white blood cells, but normal enzyme activity in all other tissues. This is compared with intermediate epimerase deficiency galactosemia, which results in decreased enzyme activity in red and white blood cells and less than 50% of normal enzyme levels in other tissues.

 

Clinically, infants with generalized epimerase deficiency galactosemia develop symptoms such as liver and renal dysfunction and mild cataracts when on a normal milk diet, while infants with peripheral or intermediate epimerase deficiency galactosemia do not develop any symptoms. Generalized epimerase deficiency galactosemia is treated by a galactose- and lactose-restricted diet, which can improve or prevent the symptoms of renal and liver dysfunction and mild cataracts. Despite adequate treatment from an early age, individuals with generalized epimerase deficiency galactosemia remain at increased risk for developmental delay and intellectual disability. Unlike patients with classic galactosemia resulting from a GALT deficiency, female patients with generalized epimerase deficiency galactosemia experience normal puberty and are not at increased risk for premature ovarian failure. Based upon reports by newborn screening programs, the frequency of epimerase deficiency galactosemia in the United States ranges from approximately 1 in 6700 African American infants to 1 in 70,000 infants of European ancestry.

 

GALM deficiency is a rare form of galactosemia that is due to a deficiency of galactose mutarotase, which may manifest clinically with bilateral cataracts. Infants with GALM deficiency have increased blood galactose concentrations with levels of galactose 1-phosphate ranging from 0.3 to 10.8 mg/dL.(1) Neonates with GALM deficiency have elevated galactose-1-phosphate, but Gal1P decreases rapidly in early infancy. To date, only pediatric patients have been described in the literature, and so the long-term, adult consequences of GALM deficiency remain unknown.

 

The incidence of GALM deficiency has been reported as 1 in 10,000 in African populations and close to 1 in 80,000 in the Japanese population, with an overall estimation of about 1:228,411 in all populations.(2)

 

See Galactosemia Testing Algorithm in Special Instructions.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Reference interval (normal range): < or =0.9 mg/dL

Therapeutic range: < or =4.9 mg/dL

Interpretation
Provides information to assist in interpretation of the test results

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

 

See Galactosemia Testing Algorithm in Special Instructions for additional information.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

No significant cautionary statements

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Wada Y, Kikuchi A, Arai-Ichinoi N, et al: Biallelic GALM pathogenic variants cause a novel type of galactosemia. Genet Med. 2019 Jun;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 Apr;126(4):362-367. doi: 10.1016/j.ymgme.2019.01.018

3. Berry GT: Classic galactosemia and clinical variant galactosemia. In: Adam MP, Ardinger HH, Pagon RA, et al. eds. GeneReviews [Internet]. University of Washington, Seattle; 2000. Updated March 9, 2017. Accessed May 3, 2021. 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 May 3, 2021. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=%20225081023

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

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

Packed red blood cells are diluted with cold water and vortexed to lyse the cells, creating a hemolysate. The hemolysate is extracted with acetonitrile/methanol containing internal standard and then is centrifuged prior to injection onto a liquid chromatography-tandem mass spectrometry (LC-MS/MS) system. The ratio of the extracted peak area of galactose-1-phosphate (Gal-1-P) to its internal standard (13)C2-Gal-1-P as determined by LC-MS/MS is used to calculate the concentration of analyte, in mg/dL, in the sample.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Thursday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

8 to 15 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 month

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

84378

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports