False Negative Tests for Urinary Glucose in the Presence of Ascorbic Acid

Abstract

Mayson, James S., Schumaker, Oma, and Nakamura, Robert M.: False negative tests for urinary glucose in the presence of ascorbic acid. Am. J. Clin. Pathol. 58: 297–299, 1972. Ascorbic acid may inhibit the glucose oxidase paper tests when present in a concentration as low as 10 mg. per 100 ml. The presence of an interfering reducing agent can be detected by adding one drop of 500 mg. per 100 ml. glucose to the test area previously dipped in the urine specimen. The incidence of false negative enzyme strip tests detected in our hospital was 1.2%. The false negative reactions are followed up with a copper reduction test, but results should be carefully interpreted, inasmuch as both glucose and ascorbic acid can give positive results.