Young children with type 1 diabetes
(less than 7 years) are highly susceptible to extreme blood glucose variability.1,2
This increased vulnerability is conferred based on several factors, including young children's increased insulin sensitivity and variability in their activity levels and food intake.1
Unfortunately, glycosylated hemoglobin A1c, a traditional measure of glycemic control, may miss glucose variability in young children because it only provides a measure of long-term average glucose levels.2,3
Similarly, in a previous study, we contend that for research purposes, the typical frequency of parents' daily self-monitoring of blood glucose (SMBG) checks may not be adequate to fully capture glucose variability in young children.3
Thus, continuous glucose monitoring (CGM) may offer the best method for measuring glucose levels in young children.
CGM is a relatively new technology that is available for clinical use and research in patients with type 1 diabetes. CGM is a nearly continuous measure of glucose levels in young children because it measures and reports a glucose level every 5
min. This can allow for a closer examination of young children's glucose patterns and may allow for better identification of glucose excursions, especially during times of the day when parents may not be regularly checking (e.g., night time).
In our past research using CGM in young children we have explored glucose variability using two new and less established measures, the Continuous Overall Net Glycemic Action (CONGA) and Mean of Daily Differences (MODD).3
The CONGA provides a measure of short-term intraday variability, whereas the MODD examines interday variability by calculating the mean of the absolute value of the difference between glucose levels measured at the same time on two consecutive days.4
Our results demonstrated that using the CONGA and MODD, young children with type 1 diabetes demonstrated greater glycemic variability than older youth with type 1 diabetes.3
In the current study, we focused on short-term glycemic variability in young children using the Average Daily Risk Range (ADRR). The ADRR is a valid, diabetes-specific measure of variability that yields a score that corresponds to a patient's risk for variability (<20, low risk; 20–40, moderate risk, >40, high risk).5
The ADRR has several advantages over the CONGA and MODD. First, the ADRR is more sensitive to hypoglycemic excursion than the other measures.4,5
This may be particularly important in young children, where excursion below the normal range could increase young children's risk for a hypoglycemic seizure.1
Second, the ADRR can be calculated using SMBG data in addition to CGM data, which may make it a more practical measure of variability than the other measures.5
Finally, there are several glucometer software programs that automatically calculate the ADRR; thus it may be more familiar to patients and to other providers.
Despite the fact that the ADRR can be calculated from SMBG data, we predict that in young children with type 1 diabetes ADRR scores calculated using SMBG (ADRRs) will be less sensitive to variability than ADRR scores calculated using CGM data (ADRRc). We base this prediction on the fact that CGM can collect more individual glucose readings per day than SMBG and even collect values overnight, when it may be more difficult for parents and young children to test regularly.3,6
If our prediction is true it will have direct implications for research and intervention studies that use glycemic variability as an outcome variable as well as implications for clinical management. Additionally, having a more accurate measure of risk for glucose variability is important in the development of the artificial pancreas and specifically in the tailoring of control algorithms for young children.7,8
Therefore, the purpose of this study was to examine both ADRRs and ADRRc data for a sample of young children with type 1 diabetes. In addition, to examine the validity of the ADRR scores using the two different data sources, we proposed to examine correlations between young children's two ADRR scores and their mean amplitude of glycemic excursion (MAGE) scores, the current gold standard for measuring variability.9,10
The two central hypotheses guiding this study were (1) young children's ADRRc scores would be more sensitive and reflect greater variability than young children's ADRRs scores and (2) young children's ADRRc scores would show better concurrent validity with MAGE scores than their ADRRs scores.