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Test ID: GALU Galactose, Quantitative, Urine

Reporting Name

Galactose, QN, U

Useful For

Screening test for galactosemia in urine specimens

Testing Algorithm

This test is not appropriate for the diagnosis or monitoring of galactosemia. For diagnosis, see GCT / Galactosemia Reflex, Blood. For monitoring, see GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes.

 

See Galactosemia Testing Algorithm in Special Instructions

Specimen Type

Urine


Advisory Information


This test is not appropriate for the diagnosis of galactosemia. For diagnosis, see GCT / Galactosemia Reflex, Blood.

 

This test is not appropriate for monitoring of galactosemia. For monitoring, see GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes.



Specimen Required


Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube: Clean, plastic urine collection container

Submission Container/Tube: Plastic, 5-mL tube (T465)

Specimen Volume: 1 mL

Collection Instructions: Collect a random urine specimen.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen (preferred) 365 days
  Ambient  20 days
  Refrigerated  20 days

Reference Values

<30 mg/dL

Day(s) and Time(s) Performed

Varies

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 U.S. Food and Drug Administration.

CPT Code Information

82760

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GALU Galactose, QN, U 2310-1

 

Result ID Test Result Name Result LOINC Value
8765 Galactose, QN, U 2310-1

Clinical Information

Galactosemia is an autosomal recessive disorder that results from a deficiency of any 1 of the 3 enzymes catalyzing the conversion of galactose to glucose: galactose-1-phosphate uridyltransferase (GALT), galactokinase (GALK), and uridine diphosphate galactose-4-epimerase (GALE). 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; even with survival, long-term intellectual disability can result.

 

Galactosemia 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. Females 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.

 

A comparison of plasma and urine galactose and blood galactose-1-phosphate (Gal-1-P) levels may be useful in distinguishing among the 3 forms of galactosemia; however, these are only general patterns and further confirmatory testing would be required to make a diagnosis.

 

 

Deficiency

Galactose (Plasma/Urine)

 

Gal-1-P (Blood)

GALK

Elevated

Normal

GALT

Elevated

Elevated

GALE

Normal-Elevated

Elevated

 

See Galactosemia Testing Algorithm in Special Instructions for additional information.

Interpretation

Additional testing is required to investigate the cause of abnormal results.

 

In patients with galactosemia, elevated galactose in plasma or urine may suggest ineffective dietary restriction or compliance; however, the concentration of galactose-1-phosphate in erythrocytes (GAL1P / Galactose-1-Phosphate [Gal-1-P], Erythrocytes) is the most sensitive index of dietary control. Increased concentrations of galactose may also be suggestive of severe hepatitis, biliary atresia of the newborn and, in rare cases, galactose intolerance.

 

If galactosemia is suspected, additional testing to identify the specific enzymatic defect is required. See Galactosemia Testing Algorithm in Special Instructions for follow-up of abnormal newborn screening results, comprehensive diagnostic testing, and carrier testing. Results should be correlated with clinical presentation and confirmed by specific enzyme or molecular analysis.

Clinical Reference

1. Berry GT: Classic Galactosemia and Clinical Variant Galactosemia. In GeneReviews. Edited by RA Pagon, MP Adam, HH Ardinger, et al. Available at www.ncbi.nlm.nih.gov/books/NBK1518/. Retrieved 03/11/2015

2. Walter JH, Fridovich-Keil JL: Galactosemia. In The Metabolic and Molecular Bases of Inherited Disease. Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York, McGraw-Hill, 2014. Accessed January 26, 2016. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&Sectionid=62672411

Analytic Time

8 days

Method Name

Spectrophotometric, Kinetic

Forms

Biochemical Genetics Patient Information (T602) in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical