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Principle: The detection is based on the de-colouration of Tillman‘s reagent. The blue coloured 2,6-dichlorophenol indophenol sodium salt is reduced to the colourless leuco form by ascorbic acid. In the presence of ascorbic acid a colour change takes place from blue to red.
Evaluation: The colour fields correspond to the following values:
0 (negative), 10 (+) and 20 (++) mg/dI
or 0 (negative), 0.6 (+) and 1.1 (++) mmol/I.
Ascorbic acid may lead to false negative results for glucose and blood. Therefore, the glucose and blood test must be repeated on positive findings for ascorbic acid, however, at the earliest 10 hours after the last vitamin C intake.
Please note: For URYXXON® Stick 10 and Combi 10® SGL normal concen-
trations of ascorbic acid (< 40 mg/dl) do not interfere, with the tests of blood and glucose.
Diagnosis: The wide spread intake of ascorbic acid (e.g. in vitamin C therapy, as a therapeutical ingredient and stabilizer of numerous medicaments, oxidation inhibitors and preservatives in food industry) causes a rapid saturation of the organism, and a renal excretion of the excess. Interfering ascorbic acid concentrations may be reached after the ingestion of fruit juice or plenty of fruit. Therefore, the ascorbic acid test zone minimizes falsely negative results. As with glucose detection, blood detection is also disturbed by low concentrations of ascorbic acid, whereas high ascorbic acid concen-trations interfere with the nitrite and bilirubin test zones.
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