Display of glucose distributions by date, time of day, and day of week: new and improved methods

Abstract

Objective: There is a need for improved methods for display of glucose distributions to facilitate comparisons by date, time of day, day of the week, and other variables for data obtained using self-monitoring of blood glucose (SMBG) and continuous glucose monitoring (CGM).

Method: Stacked bar charts are utilized for multiple ranges of glucose values, e.g., very low, low, borderline low, target range, borderline high, high, and very high. Glucose ranges for these categories can be defined by the user, e.g., <40, 40-70, 71-80, 81-140, 141-180, 181-250, and 251-400 mg/dl. Glucose distributions can be displayed by time of day, in relation to meals, by date, or by day of week. The graphic display can be generated using general purpose spreadsheet software such as Microsoft Excel or with special purpose software.

Result: Stacked bar charts are extremely compact and effective. They facilitate comparison of multiple days, multiple time segments within a day, preprandial and postprandial glucose levels, days of the week, treatment periods, patients, and groups of patients. They are superior to use of pie charts in terms of compactness and in their ability to facilitate comparisons using multiple criteria and multiple subsets of the data. One can identify episodes of hypoglycemia and hyperglycemia and can display standard errors of estimates of percentages. Interpretation of these graphs is readily learned and requires minimal training.

Conclusion: Use of stacked bar charts is generally superior to use of pie charts for display of glucose distributions and can potentially facilitate the analysis and interpretation of SMBG and CGM data.

Figure 1.

Conventional methods for display of glucose distributions. (A) Pie-charts showing the distribution of glucose values for an entire data set and for subsets corresponding to preprandial and postprandial values, bedtime and overnight. BB, before breakfast; AB, after breakfast; BL, before lunch; AL, after lunch; BD, before dinner; AD, after dinner; BT, bedtime. (B) Display of glucose by date. (C) Frequency histogram for glucose for all times of day (blue bar chart) and the corresponding cumulative frequency distribution (pink curve). (D) Display of glucose by time of day.^–, Overnight, black squares with superimposed white X; before breakfast, pink open circles; after breakfast, pink closed circles; before lunch, turquoise open triangles; after lunch, turquoise solid triangles; before dinner, brown open squares; after dinner, solid brown squares; bedtime, blue closed circles.

Figure 2.

New methods for display of glucose distribution utilizing stacked bar charts with glucose ranges and color coding as shown in Table 1.(A) Glucose distribution in relationship to meals, bedtime, and overnight, using stacked bar charts for the same data as Figure 1A. BB, before breakfast; AB, after breakfast; BL, before lunch; AL, after lunch; BD, before dinner; AD, after dinner; BT, bedtime. (B) Glucose distributions as a function of time during the continuous 24 h period. Estimates of percentages of values within any specified glucose range are obtained for a 1 h sliding time window for glucose data accumulated over a 2-week period. (C) Glucose distributions for day of the week and all days combined. (D) Glucose distributions by date for a period of one year using time as a continuous variable as in Figure 2B. This facilitates the identification of periods where there were significant problems with hypoglycemia and hyperglycemia.