What to do with the data?
The dedicated health and wellness apps typically provide average glucose and trend data but not the GMI. However, in theory users could access that metric by downloading the manufacturers’ viewing apps – for example, Clarity for Dexcom or LibreView for Libre.
Moreover, a person without diabetes could always obtain an off-label prescription from their physician for a FreeStyle Libre and purchase it at a pharmacy. At Walmart, for example, the cost for two boxes of two glucose meters with 14 days of wear each is $136.77. In that situation as well, users could download the viewing app that contains the summary data including the GMI that could potentially mislead in the setting of consistent normoglycemia.
Dr. Espinoza said: “I think there’s certainly value in glucose levels. We know the summary metrics are useful in type 1 diabetes. We don’t know which summary metrics are going to be useful in any other disease states. We may need brand new summary metrics for other disease states where it’s not about time in range. Maybe the thing that matters is the frequency or height of spikes. We don’t have a measure for that.”
He added that despite the availability of normative data, “even people without diabetes are a fairly heterogenous group. They can still have insulin resistance, so it’s tricky. From a science standpoint, we probably need studies with hundreds of patients with well-established A1c and [insulin resistance measures], weight, and body mass index. Then and only then will we be able to give an accurate glucose profile.”
In the meantime, “more data is always a good thing, but the hard thing is figuring out what do we do with it. Maybe it’s biofeedback for behavioral modification. We don’t know yet. But these are powerful tools and maybe we should learn how to use them better.”
Dr. Shah has reported receiving research grants and participating in advisory boards for Dexcom and Sanofi US. Dr. Espinoza has reported receiving research funding from the National Institutes of Health and FDA.
A version of this article first appeared on Medscape.com.