CHNS Internet Challenge

Why does vitamin C cause interference to the urine glucose test used on the reagent strip methodology? Is it positive or negative interference?

Urine Reagent Strip
Courtesy of
Virtual Hospital
Keyword Search: Restrictive Text Search of Indexed Documents
Document Search: Using the Search (or Find) Feature of Web Browser
Library Resources: ISI Citation Database

AltaVista: +"vitamin C" +"urine glucose test"
    Sixth hit: All About Urine Ketone Tests, from PlanetRx (changed to xmediapartners)
    Some key terms arise for possible use: glucose oxidase, ascorbic acid
AltaVista: +"vitamin C" +"interference" +"glucose test"
    Sixth hit: Urinalysis Standing Operating Procedure for U.S. Army Medical Dept.
    Searching through the document...

SUBJECT: SOP FOR URINALYSIS
Glucose. This test is based on a double sequential enzyme reaction. One enzyme, glucose oxidase, catalyzes the formation of gluconic acid and hydrogen peroxide from the oxidation of glucose. A second enzyme, peroxidase, catalyzes the reaction of hydrogen peroxide with a potassium iodide chromogen to colors ranging from green to brown.

High urinary ascorbic acid (vitamin C ingestion, parenteral tetracycline containing ascorbic acid as a reducing agent), gentisic acid, or homogentisic may cause false-negative results.

Confirmation?
Networked Databases from the UD Library:
ISI Citation Database, Topic: ascorbic acid AND interference AND reagent strip
ASCORBIC-ACID INTERFERENCE IN REAGENT-STRIP REACTIONS FOR ASSAY OF URINARY GLUCOSE AND HEMOGLOBIN, M. H. Zweig and A. Jackson, Clin. Chem. 32(4) 674-677, Apr. 1986.
Check DELCAT to check on library holdings...


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Last updated March 26, 2005.
© George Watson, Univ. of Delaware, 2000.