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HelpEpic Code LAB848 Carbohydrate, Urine
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
UrineOrdering 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.
Special Instructions
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, UMethod 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 daysTest 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§ionid=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.
Reducing Substances Urine