Test Catalog

Test ID: CHOU    
Carbohydrate, Urine

Useful For Suggests clinical disorders or settings where the test may be helpful

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.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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 Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


If positive, carbohydrate is identified.

Interpretation Provides information to assist in interpretation of the test results

An interpretive comment is provided.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

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.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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

Special Instructions Library of PDFs including pertinent information and forms related to the test