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Principle: The test indicates the ion concentration of urine with good correlation to the refractometric method. Increasing ion concentrations cause a colour change from blue-green via green to yellow.
Evaluation: The test allows determination of the urine density between 1.000 and 1.030. The normal value for adults with normal intake of food and liquid is from about 1.015 to 1.025; however, it can vary between 1.000 after extreme liquid intake, and 1.040 after a longer period of thirst. The density measured with test strips can vary slightly from value determined with other methods, since density increases due to glucose concentrations >1000 mg/dl (>56 mmol/l) are not covered. Increased protein excretion can result in density values, which are too high. Alkaline urines, with high contents of buffer substances, often show results, which are too low.
Diagnosis: In kidney diagnostics determination of the urine concentration is important for checking the function of the kidney parenchyma. If high liquid intake is excluded, a very dilute urine can indicate a substantial insufficiency of the kidneys, and also a lowered ability of the kidneys to concentrate the urine, which may result from Diabetes mellitus, Diabetes insipidus, Hyperaldosteronism, influence of diuretic drugs. The density of the urine yields valuable supplementary information for the evaluation of other test strip parameters, and thus helps to avoid misinterpretations, especially:
- during lysis of leukocytes and erythrocytes for interpreting possible differences with the sedimentation results
- for evaluation of the test fields for nitrite, protein and glucose
Especially in the intermediate range, between physiological and pathological results, the urine density can play the decisive role.
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