DIaMonD - A Randomized Controlled Trial Examining the Benefit of CGM Use for Adults with Type 1 Diabetes on Insulin Injections

DIaMonD Study¹ shows that Dexcom CGM use improves glucose control in adults with type 1 diabetes using insulin injections.

Background

Clinical trials demonstrating improved glucose control in patients with type 1 diabetes (T1D) using CGM have historically and predominantly involved participants who use insulin pump therapy and not insulin injections (MDI).² However, most adult patients with T1D deliver insulin by injection.³

Objective

Examine effectiveness of CGM vs. self-monitoring of blood glucose (SMBG) with blood glucose meter in adults with T1D on MDI insulin therapy.

Primary endpoint: Change in A1C

Research Design/Methods

24-week, randomized, controlled trial of 158 adults with T1D. Study conducted using the Dexcom G4 PLATINUM CGM System, which uses the same software 505 as the Dexcom G5 Mobile CGM System.

Group 1: MDI + CGM (n=105)
Group 2: MDI + SMBG (n=53)
Baseline A1C was 8.6% (range 7.5 to 9.9%)
Various education (with 45% less than a bachelor’s degree) and numeracy levels (ability to use math in daily diabetes management decisions)

Patient Education/Touchpoints

All participants received the same basic diabetes education. Intensive diabetes education and device training was not a part of this study. Study was six months in length and used a protocol with minimal “touch,” reflecting clinical practice.

Multicentered

The trial was conducted at 24 endocrinology practices in the USA (19 community-based and 5 academic centers).

Results

Dexcom CGM use resulted in a significant A1C reduction in patients with T1D on insulin injections.

In study participants using Dexcom CGM:

Overall: an average 1% A1C reduction after 24 weeks of regular use, compared to baseline (difference of 0.6% compared to SMBG group [p-value <.001]). This included:

≥1% A1C reduction for 52% of patients
Participants with a baseline A1C of ≥8.5% achieved an average of 1.3% A1C reduction compared to baseline

Diamond 1 percent A1C reduction

Dexcom CGM increased time spent in range from baseline (70 - 180 mg/dL):

CGM group: median 1.3 additional hours (+76 mins) in range
SMBG group: no increase of time in range
CGM group achieved a 4% reduction in glycemic variability compared to SMBG group

Diamond Increased Time in Range

Dexcom CGM use reduced time in hyperglycemia.

CGM group: 40% reduction of time spent in severe hyperglycemia (>300 mg/dL)*
SMBG group: median increase of 58 minutes spent in severe hyperglycemia

Diamond Reduced time in hyperglycemia

Dexcom CGM use reduced time in hypoglycemia:

37 less minutes/day <70 mg/dL; 49% reduction from baseline
20 less minutes/day <60 mg/dL; 53% reduction from baseline
14 less minutes/day <50 mg/dL; 69% reduction from baseline

Dexcom CGM use reduced nighttime hypoglycemia (<60 mg/dL):

CGM group: 79% reduction in the median time spent in hypoglycemia at night, from 2.9 to 0.6%.

Diamond Reduced time in hypoglycemia

CGM Use and Adherence

A1C reduction

A1C reductions observed with CGM use occurred independent of age, education, and diabetes numeracy.
93% of patients were using the Dexcom CGM ≥ 6 days/week (at week 24).

*Investigators pooled data from weeks 12 and 24; Δ time (median minutes/day): [pooled data - baseline data]

DIAMOND TYPE 1 STUDY HIGHLIGHTS (PDF)

1 Beck RW, Riddlesworth T, Ruedy K, et al. Effect of Continuous Glucose Monitoring on Glycemic Control in Adults With Type 1 Diabetes Using Insulin Injections: The DIAMOND Randomized Clinical Trial. JAMA. 2017;317(4):371–378. doi:10.1001/jama.2016.19975. View full article. [text link: https://jamanetwork.com/journals/jama/fullarticle/2598770]

2 Bergenstal RM, Tamborlane WV, Ahmann A, et al; STAR 3 Study Group. Effectiveness of sensor-augmented insulin-pump therapy in type 1 diabetes. N Engl J Med. 2010;363(4):311-320.

3 Grunberger G, Abelseth JM, Bailey TS, et al. Consensus statement by the American Association of Clinical Endocrinologists/American College of Endocrinology Insulin Pump Management Task Force. Endocr Pract. 2014;20(5):463-489.

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