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Test ID CHOU Carbohydrate, 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.


Forms

Biochemical Genetics Patient Information (T602) in Special Instructions.

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.

Reflex Tests

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

Testing Algorithm

Testing begins with carbohydrate analysis. If qualitative results are normal or abnormal but not indicative of galactose, testing is complete.

 

If qualitative results indicate the presence of galactose, then quantitative testing for galactose will be performed at an additional charge.

Method Name

Thin-Layer Chromatography (TLC), Qualitative

Reporting Name

Carbohydrate, U

Specimen Type

Urine

Specimen Minimum Volume

1 mL

Specimen Stability Information

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

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.

Reference Values

Negative

If positive, carbohydrate is identified.

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.

Day(s) Performed

Tuesday

Report Available

8 to 15 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

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.

CPT Code Information

84377-Carbohydrate

82760-Galactose (if appropriate)

NY State Approved

Yes