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Epic Code LAB848 Carbohydrate, Urine

Important Note

Order as Reference Miscellaneous #LAB848; indicate complete test name when ordering.

Additional Codes

Mayo Code: CHOU

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Screening for conditions associated with increased excretion of fructose, galactose, and xylose

 

This test is not recommended as a follow up test for abnormal newborn screening for galactosemia.

Specimen Type

Urine


Ordering Guidance


This test is not appropriate for evaluation of an abnormal newborn screen for galactosemia. For those cases, order GCT / Galactosemia Reflex, Blood and consider GAL1P / Galactose-1-Phosphate, Erythrocytes and GATOL / Galactitol, Quantitative, Urine.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 5 mL

Collection Instructions: Collect an early-morning (preferred) random urine specimen.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 21 days
  Refrigerated  21 days

Reject Due To

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Day(s) Performed

Tuesday

Reference Values

Negative

If positive, carbohydrate is identified.

Clinical Information

Carbohydrates are a group of mono-, di-, and oligosaccharides of endogenous and exogenous sources. Their presence frequently reflects dietary consumption but can indicate specific pathology if either a particular saccharide or a particular excretory pattern is present. Most saccharides (except glucose) have low renal thresholds and are readily excreted in the urine.

 

In addition to several other saccharide species, chromatography of urinary saccharides identifies galactose and fructose and is, therefore, useful to screen for inborn errors of galactose and fructose metabolism. Xylose may also be detected in individuals with hereditary pentosuria, a benign trait with high frequency among individuals with Ashkenazi Jewish descent.

Cautions

A number of compounds interfere with the assay and microbial contamination can lead to uninterpretable patterns of urinary saccharides. Retesting is recommended in these cases.

Interpretation

An interpretive comment is provided.

Reporting Name

Carbohydrate, U

Method Name

Thin-Layer Chromatography (TLC), Qualitative

Method Description

The urine is chromatographed on a silica gel thin-layer plate. The sugars are located with naphthoresorcinol spray reagent and are identified by visual comparison with a sugar standard chromatographed on the same plate. If galactose is found, it is quantitated by an enzymatic method.(Prinz W, Meldrum W, Wilkinson L: A simple and rapid thin-layer chromatographic method for the identification of urinary carbohydrates. Clin Chim Acta. 1978;82:229-232; Cowan T, Pasquali M: Laboratory Investigations of Inborn Errors of Metabolism. In: Sarafoglou K, Hoffman GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. 2nd ed. Elsevier; 2017:1139-1158)

CPT Code Information

84377-Carbohydrate

82760-Galactose (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CHOU Carbohydrate, U 16550-6

 

Result ID Test Result Name Result LOINC Value
9255 Carbohydrate, U 16550-6

Report Available

8 to 15 days

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.

Clinical Reference

1. Steinmann B, Gitzelmann R, Van den Berghe G: Disorders of fructose metabolism. In: Valle D, Antonarakis S, Ballabio A, Beaudet A, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease McGraw-Hill; 2019. Accessed January 09, 2020. Available at http://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=225080452

2. OMIM. #260800 Pentosuria; PNTSU. Johns Hopkins University; 1986. Updated July 9, 2016. Accessed April 23, 2021. Available at https://omim.org/entry/260800

3. Gaughan S, Ayres L, Baker P II: Hereditary fructose intolerance. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle;2015. Updated February 18, 2021. Accessed April 23, 2021. Available at www.ncbi.nlm.nih.gov/books/NBK333439

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
GALU Galactose, QN, U Yes No

Forms

Biochemical Genetics Patient Information (T602) in Special Instructions.

Laboratory Test Directory | West Additional Information:

Reducing Substances Urine