False Negative Reactions and Sensitivity in the Urine Glucose Oxidase Test

Some 6,217 random urine specimens were tested with both a glucose oxidase test (Combistix) and a copper reduction test (Clinitest). The ratio of positive Combistix to Clinitest was approximately 3 to 2. There were only eleven false negative enzyme paper tests. The qualitative reaction of the enzyme paper test was not adversely affected over a p H range of 5 to 9 or by addition of significant amounts of uric acid, creatinine, or protein. Positive two-minute Combistix reactions were noted at levels as low as 10 to 12 mg. per 100 ml. of urine glucose. Ascorbic acid completely inhibited the glucose oxidase test for at least two minutes when the ascorbic acid level was two to two and one-half times the glucose level.