The case for routinely testing the first-voided urine specimen.

A n impressive amount of evidence has accumulated in recent years documenting the importance of strict diabetic control in forestalling the microvascular complications of diabetes mel-litus. 1 " 4 This subject does not need to be reviewed here for readers of this journal. Although home glucose monitoring of capillary blood has been slowly gaining acceptance, 5 at present, the daily documentation of the degree of control in almost all diabetic patients is carried out by semiquantitative testing for glucosuria. Insulin-dependent patients usually test urine samples collected before each meal and their bedtime snack while some diabetic patients not taking insulin may test urine specimens collected within several hours of eating. In view of the data contained in references 1-3, the appropriate goal of therapy should be that all urine tests are negative for glucose. Bear in mind that glucosuria does not occur until plasma glucose concentrations exceed the renal threshold (T m) for glucose, which corresponds to plasma glucose concentrations of 160-180 mg/dl in most individuals and even higher in older subjects and those with renal disease. Whether the patient routinely tests a first-or second-voided urine sample may bear importantly on the perceived degree of control. (For those who remain skeptical about the relationship between control and some of the complications of diabetes, I refer you to Figures 9, 10, and 11 in reference 3.) Most diabetologists have usually recommended collecting and testing a second-voided urine specimen (and discarding the initial one without testing). The arguments for this position are as follows. The results of the second-voided specimen more accurately reflect the metabolic status at the time that the sample is collected. When compared with the prevailing plasma glucose concentration, the T m for glucose is evident. In addition, since the urine is not "contaminated" with glucose that may have been excreted into the bladder hours previously, the results of the second-voided specimen also more accurately reflect the effect of insulin acting at that particular time. The preprandial urine tests occur at times of peak insulin action depending on the time of injection and the type of insulin used (Table 1). Therefore, the results are helpful in adjusting insulin doses. On the other hand, missing postprandial glucosuria by only testing the second-voided specimen may lull the patient and the physician into a false sense of security that control is better than it really is. Glucosuria occurring after a meal should …