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Test Code CHOU Carbohydrate, Urine

Testing Algorithm

Qualitative testing for the presence of reducing substances is performed followed by quantitative analysis of carbohydrates including fructose, galactose, xylose, glucose, sucrose, lactose, maltose, and raffinose.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine


Ordering Guidance


This test is a quantitative analysis of carbohydrate excretion in the urine. It 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.



Necessary Information


Patient's age is required.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 5 mL

Collection Instructions:

1. Collect an early-morning (preferred) random urine specimen.

2. No preservative.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Urine Frozen 42 days

Reference Values

Reducing Substances: Negative

 

Quantitative results are reported as mmol/mol creatinine.

Age range

<12 months

12 months-18 years

≥19 years

Xylose

≤13

≤38

≤9

Fructose

≤32

≤31

≤16

Galactose

≤117

≤32

≤5

Glucose

≤139

≤15

≤22

Sucrose

≤27

≤46

≤20

Lactose

≤160

≤18

≤5

Maltose

≤5

≤1

≤2

Raffinose

≤1

≤1

≤1

Day(s) Performed

Tuesday

CPT Code Information

84379

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.

 

The identification and quantitation of carbohydrates, in particular galactose and fructose, is useful to screen for inborn errors of galactose and fructose metabolism such as galactosemia and hereditary fructose intolerance. Additionally, xylose may also be detected in individuals with hereditary pentosuria, a benign trait with high frequency among individuals with Ashkenazi Jewish ancestry.

 

This test is useful as an initial screen. To establish any diagnosis, abnormal results require confirmation by enzyme assay, molecular genetic analysis, or correlation with other laboratory testing.

Report Available

3 to 9 days

Reject Due To

Urine containing preservatives Reject

Method Name

Gas Chromatography Mass Spectrometry (GC-MS)