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Evaluation of hemoglobin AIc as a measure of diabetic control

University of British Columbia

Diabetic individuals have been found to have consistently higher levels of a minor hemoglobin component, HbAIc, than non-diabetic individuals. Previous investigators have suggested that variation in these high levels of HbAIc may be a reflection of the degree of diabetic hyperglycemia, of hypertriglyceridemia in diabetes, and of diabetic control. To date, evaluation of HbAIc as a clinically useful parameter has been hampered by the complexity of the method of measurement, the inconsistency in ranges of normal values reported, and the lack of a broad data base for comparison with new results. This investigation began with a critical appraisal of the methods currently in use for measurement of HbAIc, followed by a simplification and standardization of theJ assay. Then the levels of HbAIc in 16 non-diabetics and 47 diabetics were determined and the mean values for these 2 groups compared. The relationships between HbAIc levels in the diabetics and selected clinical data |fasting blood sugar, 24-hour urinary sugar, age,duration of illness, dietary record, insulin dosage, and family history of diabetes) were examined. Finally, the degree of diabetic control in each of the diabetic patients was estimated by the attending physician on a scale of 1 to 5 (1=very good, 2=good, 3=fair, 4=poor, 5=very poor) and was compared with the HbAIc measurement. Results of the investigation have shown that the chromatographic measurement of HbAIc is unusually sensitive to the pH of developers used and also somewhat variable with respect to the length of storage time and the optical density at which samples are read. The comparison of mean values of HbAIc for diabetics and non-diabetics has confirmed the approximately twofold higher concentration of HbAIc in diabetics. Significant correlations were found between HbAIc and fasting blood sugar (r = .442), fat content of diet (r=-. 300) , family history of diabetes (r=-.312) and degree of diabetic control (r=.529). Thus, HbAIc values tend to be higher in patients whose fasting blood sugar is high, whose diet contains relatively little fat, whose relatives are diabetic and /or whose diabetic control is poor. Correlations between HbAIc and duration of diabetes, HbAIc and insulin dosage or HbAIc and 24-hour urinary sugar were not statistically significant (r=-.131, r=-.264, r=„067, respectively). The HbAIc level appears to be an accurate reflection of fasting blood sugar levels averaged over a prolonged period of time (r=.587). In conclusion, HbAIc levels were found to provide an objective measure of diabetic control. The improved assay method makes it a practical and valuable tool for the clinician as well as the investigator. Measurement of HbAIc levels in diabetics presents a considerable advantage over currently available measures of diabetic control in assessing the long-term effectiveness of diabetic management.

Text

2010-02-21

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http://hdl.handle.net/2429/20718

Human Nutrition

University of British Columbia

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