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Test Code GATOL Galactitol, Quantitative, Urine

Performing Laboratory

Mayo Medical Laboratories in Rochester

Reporting Name

Galactitol, QN, U

Specimen Type

Urine


Necessary Information


Patient's age is required.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube (T068)

Specimen Volume: 2 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Reject Due To

Hemolysis

NA

Lipemia

NA

Icterus

NA

Other

NA

Specimen Stability Information

Specimen Type Temperature Time
Urine Refrigerated (preferred) 28 days
  Frozen  28 days

Specimen Minimum Volume

1 mL

Day(s) and Time(s) Performed

Thursday; 8 a.m.

Specimen Retention Time

3 months

Analytic Time

3 days

Reference Values

0-11 months: <109 mmol/mol creatinine

1-3 years: <52 mmol/mol creatinine

4–17 years: <16 mmol/mol creatinine

≥18 years: <13 mmol/mol creatinine

Useful For

Monitoring effectiveness of treatment in patients with galactosemia

 

Establishing a baseline level prior to initiating treatment for galactosemia

Method Name

Gas Chromatography/Mass Spectrometry (GC/MS)

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

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GATOL Galactitol, QN, U In Process

 

Result ID Test Result Name Result LOINC Value
35831 Galactitol 47857-8
35832 Interpretation (GATOL) 59462-2
35833 Reviewed By No LOINC Needed

Clinical Information

Galactosemia is an autosomal recessive disorder that results from a deficiency of 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 the GALT enzyme is life threatening. If left untreated, complications include liver failure, sepsis, cognitive and intellectual disabilities, and death. Galactosemia is treated with a galactose-free diet, which allows for rapid recovery from the acute symptoms and a generally good prognosis. Despite adequate treatment from an early age, children with galactosemia remain at increased risk for developmental delays, speech problems, abnormalities of motor function, and females 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.

 

Galactose levels may be continuously elevated in individuals affected with galactosemia even with a galactose-restricted diet regimen due to an endogenous production of galactose. The reduction of galactose to galactitol is an alternate pathway of galactose disposition when galactose metabolism is impaired. The excretion of abnormal quantities of galactitol in the urine of patients is characteristic of this disorder, and patients may have abnormal levels of galactitol even with dietary compliance. Daily consumption of galactose may cause urine levels to rise thus providing information on effectiveness of or compliance with treatment, but unlike erythrocyte galactose-1-phosphate (GAL1P) and plasma galactose, urine galactitol levels usually do not provide insight into acute and transient effects of galactose intake.

Interpretation

The concentration of galactitol is provided along with reference ranges for patients with galactosemia and normal controls.

Clinical Reference

1. Online Mendelian Inheritance in Man (OMIM). 230400, 230200, and 230350, respectively. National Center for Biotechnology Information. Accessed June 30, 2017. Available at www.ncbi.nlm.nih.gov/Omim

2. Berry GT: Classic Galactosemia and Clinical Variant Galactosemia. In GeneReviews, Edited by RA Pagon, MP Adam, HH Ardinger, et al: University of Washington, Seattle. Updated 2017 Mar 9. Available at: www.ncbi.nlm.nih.gov/books/NBK1518/

3. Walter JH, Fridovich-Keil JL: Galactosemia. In The Online Metabolic and Molecular Bases of Inherited Disease. Edited by Valle D, Beaudet AL, Vogelstein B, et al. New York, NY: McGraw-Hill, 2014. Accessed June 30, 2017. Available at http://ommbid.mhmedical.com/content.aspx?bookid=971&sectionid=62672411

Method Description

A total of 200 mcL of urine are spiked with a mixture of labeled internal standards, allowed to equilibrate, and evaporated. The dry residue is derivatized to form trimethylsilyl (TMS) esters, then extracted with hexane. Specimens are analyzed by gas chromatography/mass spectrometry, selected ion monitoring using ammonia chemical ionization and a stable isotope dilution method.(Jansen G, Muskiet F, Schierbeek H, et al: Capillary gas chromatography profiling of urinary, plasma, and erythrocyte sugars and polyols as their trimethylsilyl derivatives, preceded by a simple and rapid prepurification method. Clin Chim Acta 1986157:277-294)

Disease States

  • Galactosemia

Genetics Test Information

This test may be used as an aid in the diagnosis of galactosemia.

 

Urinary galactitol is often not affected by acute dietary ingestion of galactose; therefore, it is not a substitute for GAL1P / Galactose-1-Phosphate (Gal-1-P), Erythrocytes in monitoring diet.