Continuous Glucose Monitoring Not Just for Insulin Pumpers

Miriam E Tucker

January 24, 2017

Continuous glucose monitoring (CGM) improves glycemic control in patients with type 1 diabetes who still use multiple daily insulin injections, two new randomized clinical trials demonstrate.

Results from the 24-week DIAMOND and the 26-week GOLD studies were both published online January 24 in the Journal of the American Medical Association. DIAMOND was led by Roy W Beck, MD, PhD, of the Jaeb Center for Health Research, Tampa, Florida, and GOLD by Marcus Lind, MD, PhD, Uddevalla Hospital, Uddevalla, Sweden.

Previous studies on real-time CGM have yielded mixed results, and DIAMOND and GOLD are the first trials to specifically investigate CGM use in type 1 diabetes patients who don't wear insulin pumps, currently representing the majority of patients.

In both DIAMOND and GOLD, CGM limited both hyper- and hypoglycemia.

In DIAMOND, the magnitude of HbA1c benefit from CGM relative to usual care among insulin injection users was comparable to that found among pump users in previous randomized trials. This finding was not a foregone conclusion, Dr Beck and colleagues point out, since injection users have less flexibility in dose adjustments in response to CGM readings, with only the ability to adjust premeal bolus insulin doses.

"What we found was very profound," study coauthor Andrew J Ahmann, MD, told Medscape Medical News during the 2016 American Diabetes Association Scientific Sessions, where initial DIAMOND findings were first presented.

"I think we will find that CGM may take an earlier role in many patients. Whereas it was assumed in many patients that you would either start a pump first and CGM later, or you would start a pump with the CGM, not very often would you do the CGM first. I think that will change," said Dr Ahmann, of Oregon Health & Science University, Portland.

Some Caveats…

In an accompanying editorial, Mayer B Davidson, MD, of Charles R Drew University of Medicine and Science, Los Angeles, California, writes that the two studies "clearly show a benefit of CGM compared with [self-monitoring of blood glucose] for patients with type 1 diabetes who inject insulin," but he also noted several caveats, including the high cost of CGM relative to the modest HbA1c reduction, the short duration of the two studies, and the reluctance of some insulin-injecting patients to wear any diabetes devices.

Also, Dr Davidson points out that clinician expertise in type 1 diabetes and CGM is important in training patients to respond to the data. And he noted that the findings cannot be extended to insulin-requiring type 2 diabetes patients.

"Additional clinical trials are needed to determine the long-term effect of CGM and whether this approach translates to improved health outcomes and to determine the potential utility of real-time CGM for patients with type 1 diabetes encountered in usual clinical practice and in patients with type 2 diabetes who require insulin injections," he writes.

DIAMOND: Less Glycemic Variability With CGM

DIAMOND was a 24-week trial randomizing 158 type 1 diabetes patients on multiple daily insulin injections and baseline HbA1c of 7.5% to 9.9% to either CGM (Dexcom G4 Platinum CGM System) or self-monitoring of blood glucose (SMBG) four times daily.

The CGM group performed finger-stick measurements for confirmation before injecting insulin and twice daily for calibration, and the SMBG group wore masked CGMs.

At 24 weeks, HbA1c levels had decreased from a mean of 8.6% at baseline in both groups by 1.0 percentage points with CGM vs 0.4 with SMBG, a significant 0.6-percentage-point difference (P < .001). The proportions with HbA1c below 7.0% at study end were 18% with CGM vs 4% SMBG (P = .01).

Masked CGM in the SMBG group revealed that the time spent in glucose ranges of 70 to 180 mg/dL were significantly higher and in levels above and below that range significantly lower, with CGM compared with SMBG. Overall, glycemic variability was 4% less with CGM.

Severe hypoglycemia occurred in two patients in each group. No patients experienced diabetic ketoacidosis. The CGM patients reported high levels of satisfaction with the device.

GOLD: A Crossover Study

GOLD was a crossover randomized clinical trial of 161 patients using multiple daily insulin injections with baseline HbA1c levels of at least 7.5% (mean, 8.6%) that also compared CGM with SMBG. All underwent two 26-week study periods with each of the approaches, with a 17-week washout period in between.

At the end of the intervention periods, HbA1c levels were 7.9% with CGM vs 8.3% with SMBG alone, a significant 0.4-percentage-point difference (P < .001).

Masked CGM in the SMBG group demonstrated that the CGM group spent 52 fewer minutes a day outside the 70- to 180-mg/dL target range, as well as less time with glucose levels above and below the target range, and reduced glycemic variability.

There was one severe hypoglycemia event in the CGM group and five in the SMBG only group (not significantly different), and seven hypoglycemia events during the washout phase.

Here again, patients reported greater satisfaction with CGM on questionnaires assessing well-being, treatment satisfaction, diabetes distress, and hypoglycemia fear/confidence (all P < .001).

Dr Ahmann told Medscape Medical News, "There are pretty good indications that continuous glucose monitoring appears to be improving quality of life. I hope that that will become evident through the science as well."

DIAMOND was funded by Dexcom. Dr Beck reports receiving a study grant from Dexcom and that his institution received supplies for research from Dexcom and Abbott Diabetes Care for other studies. Dr Ahmann reports receiving grants for the study and consulting for Dexcom; receiving grants for research support from Medtronic, Novo Nordisk, Lexicon, and Sanofi; consulting for Novo Nordisk, Sanofi, and AstraZeneca; and serving on advisory boards for Lilly, Janssen, and AstraZeneca. Disclosures for the coauthors are listed in the paper. GOLD was funded by the NU Hospital Group, Trollhättan and Uddevalla, Sweden. Dr Lind reports receipt of grants from AstraZeneca, Dexcom, and Novo Nordisk; consulting and receipt of honoraria from Novo Nordisk and Rubin Medical; and lecturing for Eli Lilly, AstraZeneca, Novo Nordisk, Medtronic, and Rubin Medical. Disclosures for the coauthors are listed in the paper. Dr Davidson has no relevant financial relationships.

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JAMA. Published online January 24, 2017. DIAMOND study, GOLD study, Editorial

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