Slicing the Pie: Correlating HbA1c values with average blood glucose values in a pie chart form

Abstract

OBJECTIVE The purpose of this study was to define the correlation between HbA1c values and the percentage of home blood glucose (HBG) measurements within given ranges in a pie chart in three age-groups of subjects with type 1 diabetes. RESEARCH DESIGN AND METHODS HbA1c values were compared with HBG measurements in subjects who did at least three blood glucose tests per day over 30 days in three age-groups: 5–11, 12–16, and 17–35 years. The blood glucose values were arbitrarily divided into three groups, defined as the percentage of HBG measurements within, above, and below target range. Each range was then compared with the corresponding HbA1c value. Longitudinal data were also collected for 279 of the subjects after a mean of 139 days. RESULTS A strong correlation (P = 0.001) was found between HbA1c values and the average blood glucose, and also with the percentage of HBG measurements within, above, and below target range in each of the three age-groups (P < 0.001). Analyses of longitudinal data showed a strong correlation of the changes in HbA1c values to the changes in blood glucose values. CONCLUSIONS These data showed that a pie-shaped graph of the HBG data can be useful as a clinical parameter in helping patients and families attain desired HbA1c values.