Diabetes Technology Highlights

DEXCOM’S DIAMOND STUDY SHOWS CGM BENEFITS MDI AT SIX MONTHS: STRONG -0.6% A1C ADVANTAGE, +61 MORE MINUTES IN RANGE PER DAY

Joslin’s Dr. Elena Toschi reported positive results from Dexcom’s DIaMonD study, which randomized MDI users to six months of CGM (n=105) or six months of usual care (n=53).

HbA1c declined a strong 0.9% with CGM at six months vs. -0.4% with usual care (baseline: 8.6%), for an adjusted mean difference of -0.6% in favor of CGM (p<0.001). 

From press release Dexcom.

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The advantage for CGM was impressively consistent across age, baseline hypoglycemia, education, and diabetes numeracy – 60+ year-old CGM users saw the same benefit as 25-60 year-old users in this study

At the same time HbA1c declined, hypoglycemia significantly improved with CGM: a 30% improvement in time <70 mg/dl (-23 mins/day; p=0.006) and a strong 50% improvement in time <50 mg/dl (-11 mins per day; p=0.005), both outperforming 17% and 21% improvements with usual care (-15 mins, -6 mins).

While the absolute reductions are not huge here, the high HbA1c baseline patients were not experiencing an overwhelming amount of hypoglycemia at baseline.

On the high end, CGM users were spending 83 fewer minutes per day above range (>180 mg/dl) at 24 weeks, while the usual care group was spending nine more minutes per day above range (p=0.04). That translated to CGM users spending an hour more per day in range (70-180 mg/dl ) at 24 weeks, while the usual care group spent 15 fewer minutes per day in range (p=0.006). CGM trended towards less severe hypoglycemia: a 2% rate (two out of 105 patients) vs. a 4% rate in usual care (two out of 53 patients). 

Glycemic variability also significantly improved with CGM (median CV: 42% to 38%), but did not change in usual care (42% to 42%) (p<0.001). 

Daily SMBG tests declined as expected in the CGM group (from 5.1/day to 3.6/day), but stayed roughly similar in the usual care group (5.1/day to 4.6/day) (p<0.001). CGM wear >6 days per week was seen in an impressive 89% of patients at six months, a testament to the better technology and the tight adherence criteria (>85% wear) patients had to demonstrate during the blinded CGM phase before randomization.

The presentation said the “latest” Dexcom CGM was used, which we assume means the G4 sensor with Software 505. More study details below.

• Overall, these are very strong and positive results for Dexcom and the entire CGM field, which has given most of its data around patients on pumps for years. The DIaMonD shows that MDI users not at glycemic target can get a meaningful reduction in A1c (-0.9% or 9 mmol/mol from baseline), shave off highs, cut their time in mild and dangerous hypoglycemia, and improve variability.
• We hope this large randomized study can help influence more prescribing of CGM in MDIs, and more importantly, influence professional guidelines. DIaMonD is also a milestone for Dexcom, who has never run an outcomes study, and will need to do more to keep up with Medtronic’s and Abbott’s growing lists.
• Dr. Howard Wolpert succinctly summarized the positive implications of the DIaMonD study results: “Clinicians should consider recommending CGM to all patients with type 1 diabetes who have not attained their glycemic goals.” He noted the consistency of these HbA1c outcomes with the JDRF CGM trial and STAR-3 trials (~0.5% reduction), but with fewer in-clinic visits than in either trial (see below). 
• Dr. Wolpert also pointed out the high sensor adherence (89% wore >6 days per week) in DIaMonD, which exceeded usage in other CGM studies (e.g., in STAR 3, only 23% used the CGM >80% of the time). CGM compliance, said Dr. Wolpert, is all about the tradeoff between benefits and demands – with better technology now (accurate, reliable, easier to use), the benefits are starting to outweigh the hassles for more patients.
• Indeed, Dr. Wolpert characterized the glucose-monitoring field as “at an inflection point.” The transition from urine testing to intermittent fingersticks in the DCCT era reduced A1c, but increased hypoglycemia. Now we’re making the transition from intermittent fingersticks to CGM, which reduces A1c and brings fewer hypoglycemia events. 
• To close his remarks, Dr. Wolpert noted that among MDI users in the T1D exchange, 93% are using SMBG alone, and 7% are using CGM. This large randomized study supports the benefits of CGM in those on MDI, and hopefully, will drive further penetration of the technology in MDIs.