TABLE 2.

Advantages and Disadvantages of Using Composite Metrics for Analyzing Continuous Glucose Monitor Data

Features of composite metrics	Advantages	Disadvantages
How composite metrics are used in medicine	Composite metrics have been successfully used in other fields of medicine and outside of medicine	For each component of a composite metric that is to be scored on a range of quality, these ranges are arbitrarily assigned. There is no agreement on the cutoffs for scoring noncontinuous discrete metrics that are components of a composite metric. For example, hypoglycemia or hyperglycemia can be defined at various cutoff levels for these states and these are common components for composite metrics.
Selection of composite metrics	Compared to AGP or the long list of various CGM parameters/components that have been proposed to define good glycemic control, a simple composite metric may be sufficient to support a conclusion that a patent is doing well. If the patient is doing poorly, then each of the component metrics can be studied to provide focused therapy intended to improve glycemic control.	There is currently no consensus on the optimal metric for assessing glycemic variability. The International Consensus suggests using CV rather than SD or GVP.
Benefits of using composite metrics	Compared to HbA1c, a composite metric may provide a better assessment of glycemic control, by also considering important parameters of glycemia, such as glucose variability, TIR, severity and duration of hypoglycemia. These are metrics that are not fully accounted for when only HbA1c, reflecting mean glucose, is used.	So far, no composite metric has been tested against another to address which metric is the best for assessing quality of glycemic control in long-term prospective outcome studies.
Clinical applications	The majority of patients with diabetes are managed by primary care physicians. A composite metric may help these professionals to identify patients that have acceptable or inappropriate glycemic control, directing them to focus mainly on the latter group.	There is some overlap in components used between composite metrics but there is no consensus on which components are necessary to consider when treating patients. There is also no agreement on how a set of multiple component metrics should be weighted within a composite metric.
Reasons for using composite metrics	Considering that many physicians must evaluate patients with diabetes in less 15–20 min in a typical clinic visit, a composite metric can provide a rapid assessment of glycemic control, allowing these professionals to focus on other areas (such as education, a healthy lifestyle, a healthy diet, and proper use of technology).	There are limited clinical data with objective outcomes assessing the minimum safe percentage of time spent in the target range (also known as TIR)23,38 although an expert consensus panel recently recommended at least 70% of the time patients should be time in a range of glucose concentrations 70–180 mg/dL.38
How CGM composite metrics are linked to the use of CGM	CGM is increasingly being prescribed by diabetes HCPs and covered by insurers.	Calculation of the described composite metrics requires the use of CGM, which some patients with diabetes may not be able to afford or need to use (for example patients treated with some oral antidiabetic medications)
How CGM component metrics are linked to long-term outcomes	Cross-sectional data suggest that TIR, measured with CGM, which is a component of recent composite metrics, is inversely associated with the prevalence of diabetic retinopathy44 and carotid intima media thickness45	Composite metrics have not been tested for their relationship to predicting long-term complications. HbA1c remains the best validated prognostic marker of long-term diabetes complications.

AGP, Ambulatory Glucose Profile; CGM, continuous glucose monitor; HCPs, health care professionals.