Interpreting the ambulatory glucose profile

Abstract

A systematic approach to interpreting dense glucose data from continuous glucose monitoring (CGM) systems is important for dealing with the daunting amount of data that these systems provide. Moreover, a consensus approach would be useful to reduce differences in interpretation of similar data between physicians. The ambulatory glucose profile (AGP), now available for the FreeStyle Libre flash glucose monitoring system and some CGM systems, allows simpler and more confident identification of patterns, by averaging data for the modal day (itself derived from several daily CGM traces). Its output provides a single curve representing the average, with interquartile and interdecile ranges. Even scattered individual data values without discernible pattern can be averaged and produce useful clinically relevant information, especially where there is considerable glycaemic variability. Consensus recommendations on the use of the AGP build on an understanding of the user's daily routine, followed by examination of the AGP for periods of hypoglycaemic risk, i.e. when the 10th centile line for glucose approaches or enters the hypoglcycaemic range. These analyses are supported by the glucose pattern insights analysis available from the FreeStyle Libre flash glucose monitoring system, which flags up the likelihood of low glucose, the proximity of the median glucose to target, and the degree of variability below the median at various times of day. Where hypoglycaemia patterns are not apparent, the consensus guidance recommends assessing the periods around overnight, morning meal, midday meal, and evening meal in turn. In these ways, the consensus guideline provides the systematic approach to interpretation which is the cornerstone of using the AGP.