Table 1

GV metrics at a glance

GV metricDefinitionClinical implications of GV metric*Normal reference range (2 SD around mean)
SDThe amount of variation or dispersion of a data set. The SD of the data set is the square root of its variance.Variation measure most familiar to clinicians and easy to calculateSDT 10–26 mg/dL
At least eight subtypes of SD: the three most commonly used are 1) overall (total) SD, SDT (SD of all data, all days); 2) within-day SD, SDW (average of SD for each day); and 3) between-day SD, SDdm (SD of the daily means of each day)Most accurate if values are “normally distributed around the mean,” which is often not the case
%CVThe extent of variability in relation to the mean of the populationLess influenced when comparing data sets with widely different mean glucose values (or HbA1c)19–25%
100 × SD/mean of the observationsPossibly the “best” single research measure to compare GV over time or between data sets
IQRThe spread of values 25% above and 25% below the median, sometimes called the middle fiftyLikely the “best” metric for visualizing GV around the median glucose curve13–29 mg/dL
Plotting the IQR (around the median glucose curve) on a modal day glucose profile makes it is easy to spot what time of day has the most GV and needs attention
Mean amplitude of glycemic excursionsAverage of all blood glucose excursions or swings (peak to trough) that are greater than 1 SD of all measures for a given glucose profileMost common measure of glucose spikes, swings, or excursions as opposed to glucose dispersion41 and 48 mg/dL# (results from day 1 and 2 for one normal individual using CGM for 48 h)
Used for many years; can be applied to SMBG or CGM data
Continuous overall net glycemic action (1–24 h)Intraday (within-day) glycemic variationNo clear benefit of these measures compared with the four more commonly used measures listed aboveFew normal studies
CONGA (1–24 h)The standard deviation of the differences of glucose readings for a defined period of hours
Mean of daily differencesInterday (between-day) glycemic variation
The absolute value of the difference between glucose values taken on two consecutive days at the same time
Mean absolute differenceMean absolute difference of consecutive blood glucose values derived from SMBG data performed five times per 24 h
Mean absolute glucoseThe summed differences between sequential 7-point SMBG profiles per 24 h divided by the time in hours between the first and last blood glucose measurement
  • * Author’s assessment/opinion,

  • per Mazze et al. (8),

  • # per Service (22).