Urine Diagnostics / Urine Test Strips / Portfolio Urine Test Strips / Ketones
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| Test principle | |
 |
Aceto acetic acid and acetone react with sodium nitroprusside in an alkaline medium to form a violet colour complex (Legal's test). |
| Sensitivity |
| The test field is more sensitive to aceto acetic acid (>5 mg/dl, 0.5 mmol/l) than to acetone (>30-50 mg/dl). |
| Specivity |
| The comparable colour scale is set for aceto acetic acid. |
| Sources of errors |
| High concentrations of phenolpyruvic acid gives a different coloration. Phthaleins and anthraquinone derivates display a red colouration in the alkaline range, which can cover up the evidence. ß-Hydroxybutyric acid is not detected. Phthalein compounds produce reddish colours. |
| Significance |
| The collective term "ketones" or "ketone bodies" is used in medicine to denote the three substances acetoacetate, ß-hydroxybutyrate and acetone. Ketone bodies occur in cases of decompensated carbohydrate- fat metabolism 1). A lack of glucose processing causes increased lipolysis and thus a rise in free fatty acid levels in the serum. The acetyl-coenzyme A produced during degradation in the liver is only partly further processed. The surplus reacts to form acetoacetic acid, which is partly eliminated via the kidneys. At the same time ß-hydroxybutyric acid can form due to reduction and acetone due to decarboxylation. These three substances always occur in urine together (ratio of acetone: aceto-acetic acid 1:10). Ketone bodies are detected in urine by recording the aceto-acetic acid level. There is no clear relationship between ketonuria and the ketone content in blood.Urine does not normally contain ketone bodies. Detectable concentrations of ketones can also be caused by physiologic exertion (fasting, pregnancy, sport). Ketone detection in urine is particularly important for detecting metabolic decompensation in diabetes mellitus. |
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