This review examines the current status of the clinical evaluation of diabetic control. The assessment of the patient's symptoms and signs is important but requires laboratory confirmation. Major metabolic derangements usually occur before their clinical detection is feasible.
To be complete, the laboratory assessment of diabetic control should include the insulin concentration in blood or urine. At present insulin and other hormones assays have played mainly an investigative role.
Glucose measurements in blood and urine continue to be the standards for evaluation of diabetic control. Glucose tolerance tests or carefully timed preprandial and postprandial plasma glucose measurements on several successive days under consistent conditions of diet and exercise provide data for adequate evaluation of diabetic control. The addition of urinary glucose monitoring to the blood sampling makes the evaluation more complete. Glucose variability measurements in blood and/or urine provide useful data for characterizing patients, for comparing them with other diabetics, with nondiabetic normals, and with themselves from time to time.
Despite their limitations, urine glucose tests are valuable and worth evaluating so as to provide for each patient the most appropriate method of testing. Methods are described for screening patients for atypical blood-to-urine glucose relationships (“renal glucose threshold”) and for estimating such thresholds.
Among lipid metabolic indices of insulin deficiency the urinary ketone bodies are the most commonly measured in clinical medicine. Triglycerides and cholesterol elevations may in part reflect disturbed diabetic control and may warrant a trial of intensified antidiabetic therapy.
The protein metabolic changes of diabetes during hyperglycemia are measurable as decreased levels of plasma alanine and increased levels of branched-chain amino acids. By sensitive quantitative methods, albuminuria is also demonstrably increased during impaired diabetic control. Improved diabetic regulation restores these protein abnormalities toward normal. These newer refinements for evaluating diabetic control await clinical application.
Glycosylation of hemoglobin, identifiable by an increased proportion as hemoglobin A1c, is of special interest as a longer-term indicator of hyperglycemia.
As clinical interest in more complete normalization of diabetic metabolic changes is intensifying, a wider array of methods are becoming available for determining the degree to which metabolic control is normalized.