| Specimen requirement | Spot urine: Plain urine bottle Minimum volume: 5 mL |
| Authorisation code required | No |
| 24 Hr available service | No |
| Method | Reduction of cupric to cuprous ions in alkaline solution |
| Reference interval | Normal: negative |
| Clinical indication | Detection of non-glucose reducing substances that are not detected by specific tests for glucose (e.g. screening for galactosaemia / galactosuria). |
| Result interpretation |
Galactose, fructose and glucose are the urinary reducing substances that are of pathological significance. The commonest cause of a positive result is glucosuria. If the test is positive in a baby, but a specific test for glucosuria is negative, further testing for galactosaemia should be done and lactose removed immediately from the diet, pending the test results. Glucose appears in urine in diabetes mellitus and in renal tubular dysfunction. Galactose appears in urine in galactosemia, the major cause of which is an inherited deficiency of galactose-1-phosphate uridyl transferase. The disease causes liver enlargement, cataract, and mental retardation, and can be alleviated by withholding foods containing galactose, e.g. cow milk and dairy products from the diet. Fructose appears in urine in patients with fructose intolerance. The test is positive in alkaptonuria due to the presence of homogentisic acid. A number of drugs and unusual dietary sugars may give positive results. |
| Measurement of uncertainty | See table. |
| Frequency of measurement | Daily |