Mixed results from adding insulin pump to CGM in type 1 diabetes
medwireNews: A analysis from the DIAMOND trial suggests that adding an insulin pump to continuous glucose monitoring (CGM) leads to better glycemic control, but at the price of more hypoglycemia.
The DIAMOND trial, which, along with the GOLD trial, recently published its primary findings, demonstrated the benefits of CGM for adults with type 1 diabetes using multiple daily injections. This latest study involved 75 patients from the CGM group who, having completed the main DIAMOND trial, were randomly assigned to either continue with daily injections or switch to using an insulin pump, in addition to continued CGM.
Switching to an insulin pump significantly improved patients’ glucose control according to the primary outcome of CGM-measured time with glucose levels between 70 and 180 mg/dL (3.9–10.0 mmol/L), at a median of 791 minutes/day compared with 741 minutes/day for continued daily injections, largely accounted for by improvements in daytime glucose control.
“The benefit of [insulin pump use] on glycaemic control was most evident in participants who started this trial with worse glycaemic control—ie, those who had the greatest room for improvement,” write Roy Beck (Jaeb Center for Health Research, Tampa, Florida, USA) and study co-authors in The Lancet Diabetes & Endocrinology.
Patients with baseline glycated hemoglobin (HbA1c) levels of 7.5% or higher achieved an 11% improvement in time spent in normoglycemia with insulin pump treatment, both versus baseline and versus the control group, whereas those with better glucose control at baseline did not see any additional benefit.
However, a supplemental analysis showed that patients with higher baseline HbA1c levels also increased their time in hypoglycemia, by 1.3% when they switched to using an insulin pump, compared with a 1.3% reduction among patients who had good glycemic control at baseline.
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In the main analysis, there was a significant increase in the time spent in hypoglycemia among patients assigned to insulin pump treatment, from a median of 34 to 49 minutes per day (at <70 mg/dL; 3.9 mmol/L), which did not occur in patients who continued to use daily injections. But the researchers stress that even with this increase, patients remained well below the 73 minutes per day median recorded at enrollment to the main DIAMOND trial.
Beck and team speculate that the increased hypoglycemia with the addition of an insulin pump reflected tighter glycemic control, but add that it could also result from “inappropriate management” of pump therapy.
Of note, the improved glycemic control according to CGM glucose levels was not matched by improvements in HbA1c levels. However, Roman Hovorka (University of Cambridge, UK), the author of an accompanying commentary, believes that increased use of CGM may prompt a shift back to using mean glucose levels, for which HbA1c is a surrogate.
“What is not always appreciated is that HbA1c represents a weighted mean of glucose over the previous 2–3 months, skewed towards most recent glucose values, whereas sensor-based metrics are not susceptible to such an imbalance,” he says.
Given the excellent accuracy of modern sensors, and their high use in studies such as DIAMOND, he says: “It would be difficult to argue that sensor-based metrics do not reflect true glucose concentrations.”
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