Glucose Apart from glucose, no other compound in urine is known to give a positive reaction. False positive reactions can be produced by a residual of oxidative compounds, from cleansing agents, for example. Larger amounts of vitamin C (e.g. from tablets, antibiotics or fruit juices) can result in lower or false negative results.

Ketones Urine ketone bodies include acetoacetic acid, acetone and beta-hydroxybutyric acid, and they are produced exclusively in the liver. Ketones in the urine signalize an abnormal carbohydrate metabolism.

Beta-hydroxybutyric acid is not detected, as it is not a ketone. Phenylketones in higher concentrations interfere with the test by producing variable colors. Phthalein compounds interfere by forming a red color.

Protein The Protein test pad contains changes color in the presence of albumin. Other urine proteins are indicated with less sensitivity (e.g. globulins, mukoproteins, hemoglobin, Bence-Jones protein).

The protein test is not influenced by the urine physiological range of pH values, but in strongly alkaline urine (pH >8) or in urines with extremely high buffering capacity, the test can provide false positive results.  In addition, the presence of polyvinylpyrrolidone (blood substitute), quinine or the disinfectants residue (quat-based) can lead to false positive results. The residues of disinfectants on the base of nonionic or anionic detergents can also cause false negative results.

pH The pH value of fresh urine from healthy individuals varies from a pH of 5 and 6 to a pH of 8, depending on the individual’s food intake. Prevalence of meat products in the diet lead to a more acidic pH level, while a lacto-vegetable diet causes more alkaline urine with a pH greater than 7. Any inorganic acidic or alkaline substances presented in urine can interfere with the test.