Background and Aims

To contrast the total and within-day coefficient of variation for glucose (CV) thresholds to guide clinical assessment of glucose variability and hypoglycemic exposure.

Methods

De-identified data provided glucose readings from 1,002,946 flash glucose monitor users. The total and within-day CV and daily scan rate for each reader were found. Readers were grouped by ten equal groups of scan rate, then quartile groups by t-CV and wd-CV were found, for 25,074 readers per group. The association of glucose variability and time below range (TBR) was examined by median time below 54 mg/dL and t-CV and wd-CV.

Results

The association of glucose variability and hypoglycemia was examined as shown in Figure 1. As expected, the wd-CV is always less than the t-CV at any given level of hypoglycemia exposure. Both wd-CV and t-CV were associated with time below 54 mg/dL. In order to achieve the consensus target of < 1% time below 54 mg/dL, the associated wd-CV and t-CV values are 33.5% and 39.5%, respectively.

Conclusions

Health care professionals should be aware of the type of CV reported by the different CGM systems. To our knowledge, the CV calculated in the majority of CGM reports is the t-CV. Then, appropriate thresholds should be used to identify patients likely to meet TBR targets (t-CV < 39.5% or wd-CV <33.5%).

Figure 1: Association of glucose time below 54 mg/dL and glucose variability measured by t-CV and wd-CV. Quartile groups of wd-CV (cross signs) and Total CV (open circles, red=lowest, magenta = highest). N=1,002,946 readers, each point is 25,074 readers.