Could glycaemic control be based on urine glucose determination

Glucose is freely filtered by renal glomeruli and completely reabsorbed in the proximal convoluted tubules. When, however, glucose concentration in the plasma exceeds approximately 180 mg/dl (10.0 mmol/L), tubular reabsorption is incomplete. Thus, glucose concentration in the urine is proportional to the increase of glucose in the plasma above 180 mg/dl (10.0 mmol/L).

There are special reagent strips used for detection of glucose in the urine. However, this method of glycaemic control evaluation, although simple, painless and cheap, has some major disadvantages:

• Renal threshold varies among people (even within the same person); as a consequence, when the threshold is high, people with significant hyperglycaemia can exhibit no glucosuria (for example, patients with long-standing diabetes), and when the threshold is low, glucosuria can be present even in persons with normal blood glucose values (for example, children and pregnant women).

• Renal threshold increases with age.

• Renal threshold is affected by the body's hydration status.

• Glucose concentration in the urine does not represent glycaemia at the time of determination.

• Even if renal threshold were to be steady at a level of 180mg/dl (10.0 mmol/L), glucose determination in the urine would not be able to discern between hypoglycaemia, normoglycaemia and mild hypergly-caemia.

For all these reasons, self monitoring of glucose in the urine is now indicated only for persons who refuse or are unable to use a portable glucose meter for home capillary blood glucose measurements. It could only be accepted for persons with mild and controlled Type 2 DM, who do not receive insulin, and perform regular measurements of plasma glucose and HbAlc at a laboratory.

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