Feasibility of 10-day use of a continuous glucose-monitoring system in adults with type 1 diabetes

Emerging Diabetes Technologies: Continuous Glucose Monitors/Artificial Pancreases

Over the past decade there have been many advances in diabetes technologies, such as continuous glucose monitors (CGM s), insulin-delivery devices, and hybrid closed loop systems . Now most CGMs (Medtronic-Guardian, Dexcom-G6, and Abbott-Libre-2) have MARD values of < 10%, in contrast to two decades ago when the MARD used to be > 20%. In addition, the majority of the new CGMs do not require calibrations, and the latest CGMs last for 10-14 days. An implantable 6-months CGM by Eversense-3 is now approved in the USA and Europe. Recently, the FDA approved Libre 3 which provides real-time glucose values every minute. Even though it is approved as an iCGM it is not interoperable with automatic-insulin-delivery (AID) systems. The newer CGMs that are likely to be launched in the next few months in the USA include the 10-11 days Dexcom G7 (60% smaller than the existing G6), and the 7-days Medtronic Guardian 4. Most of the newer CGM have several features like automatic initialization, easy insertion, predictive alarms, and alerts. It has also been noticed that an arm insertion site might have better accuracy than abdomen or other sites, like the buttock for kids. Lag time between YSI and different sensors have been reported differently, sometimes it is down to 2-3 min; however, in many instances, it is still 15-20 min, especially when the rate of change of glucose is > 2 mg/min. We believe that in the next decade there will be a significant increase in the number of people who use CGM for their day-to-day diabetes care.

Cost-effectiveness of Initiating an Insulin Pump in T1D Adults Using Continuous Glucose Monitoring Compared with Multiple Daily Insulin Injections: The DIAMOND Randomized Trial

BACKGROUND

The economic impact of both continuous glucose monitoring (CGM) and insulin pumps (continuous subcutaneous insulin infusion [CSII]) in type 1 diabetes (T1D) have been evaluated separately. However, the cost-effectiveness of adding CSII to existing CGM users has not yet been assessed.

OBJECTIVE

The aim of this study was to evaluate the societal cost-effectiveness of CSII versus continuing multiple daily injections (MDI) in adults with T1D already using CGM.

METHODS

In the second phase of the DIAMOND trial, 75 adults using CGM were randomized to either CGM+CSII or CGM+MDI (control) and surveyed at baseline and 28 weeks. We performed within-trial and lifetime cost-effectiveness analyses (CEAs) and estimated lifetime costs and quality-adjusted life-years (QALYs) via a modified Sheffield T1D model.

RESULTS

Within the trial, the CGM+CSII group had a significant reduction in quality of life from baseline (-0.02 ± 0.05 difference in difference [DiD]) compared with controls. Total per-person 28-week costs were $8,272 (CGM+CSII) versus $5,623 (CGM+MDI); the difference in costs was primarily attributable to pump use ($2,644). Pump users reduced insulin intake (-12.8 units DiD) but increased the use of daily number of test strips (+1.2 DiD). Pump users also increased time with glucose in range of 70 to 180 mg/dL but had a higher HbA1c (+0.13 DiD) and more nonsevere hypoglycemic events. In the lifetime CEA, CGM+CSII would increase total costs by $112,045 DiD, decrease QALYs by 0.71, and decrease life expectancy by 0.48 years.

CONCLUSIONS

Based on this single trial, initiating an insulin pump in adults with T1D already using CGM was associated with higher costs and reduced quality of life. Additional evidence regarding the clinical effects of adopting combinations of new technologies from trials and real-world populations is needed to confirm these findings.

Cost-effectiveness of Continuous Glucose Monitoring for Adults With Type 1 Diabetes Compared With Self-Monitoring of Blood Glucose: The DIAMOND Randomized Trial

OBJECTIVE

This study evaluated the societal cost-effectiveness of continuous glucose monitoring (CGM) in patients with type 1 diabetes (T1D) using multiple insulin injections.

RESEARCH DESIGN AND METHODS

In the Multiple Daily Injections and Continuous Glucose Monitoring in Diabetes (DIAMOND) trial, 158 patients with T1D and HbA_1c ≥7.5% were randomized in a 2:1 ratio to CGM or control. Participants were surveyed at baseline and 6 months. Within-trial and lifetime cost-effectiveness analyses were conducted. A modified Sheffield T1D policy model was used to simulate T1D complications. The main outcome was cost per quality-adjusted life-year (QALY) gained.

RESULTS

Within the 6-month trial, the CGM group had similar QALYs to the control group (0.462 ± 0.05 vs. 0.455 ± 0.06 years, P = 0.61). The total 6-month costs were $11,032 (CGM) vs. $7,236 (control). The CGM group experienced reductions in HbA_1c (0.60 ± 0.74% difference in difference [DiD]), P < 0.01), the daily rate of nonsevere hypoglycemia events (0.07 DiD, P = 0.013), and daily test strip use (0.55 ± 1.5 DiD, P = 0.04) compared with the control group. In the lifetime analysis, CGM was projected to reduce the risk of T1D complications and increase QALYs by 0.54. The incremental cost-effectiveness ratio (ICER) was $98,108 per QALY for the overall population. By extending sensor use from 7 to 10 days in a real-world scenario, the ICER was reduced to $33,459 per QALY.

CONCLUSIONS

For adults with T1D using multiple insulin injections and still experiencing suboptimal glycemic control, CGM is cost-effective at the willingness-to-pay threshold of $100,000 per QALY, with improved glucose control and reductions in nonsevere hypoglycemia.

A review on B-type natriuretic peptide monitoring: assays and biosensors

Since its discovery in 1988, B-type natriuretic peptide (BNP) has been recognized as a powerful cardiovascular biomarker for a number of disease states, specifically heart failure. Concurrent with such a discovery, much effort has been allocated to the precise monitoring of physiological BNP levels. Thus, it can be used to guide the therapy of heart failure and determine the patient's stage of disease. Thus, we discuss in this article BNP as a potent biomarker. Subsequently, we will review the progress of biosensing devices as they could be applied to monitor BNP levels as assays, benchtop biosensors and implantable biosensors. The analytical characteristics of commercially available BNP assays are presented. Still emerging as a field, we define four obstacles that present opportunity for the future development of implantable biosensor: foreign body response, sensor renewability, sensitivity and selectivity.

Glucose Variability in a 26-Week Randomized Comparison of Mealtime Treatment With Rapid-Acting Insulin Versus GLP-1 Agonist in Participants With Type 2 Diabetes at High Cardiovascular Risk

OBJECTIVE

A1C is associated with diabetes complications but does not reflect glycemic variability (GV), which may worsen outcomes by inducing inflammation, oxidative stress, and cardiac arrhythmias. We tested whether a glucagon-like peptide 1 agonist-based regimen can reduce GV and cardiometabolic risk markers while maintaining similar A1C levels in people with insulin-requiring type 2 diabetes and high cardiovascular risk.

RESEARCH DESIGN AND METHODS

After run-in on metformin and basal-bolus insulin (BBI), 102 participants continued metformin and basal insulin and were randomized to exenatide dosing before the two largest meals (glucacon-like peptide-1 receptor agonist and insulin [GLIPULIN group]) or continuation of rapid-acting insulin analogs (BBI group). Indices of GV by continuous glucose monitoring (CGM), hypoglycemia, weight, risk markers, and cardiac arrhythmias were assessed. The primary end point was change in glucose coefficients of variation (CV) by CGM from baseline to 26 weeks.

RESULTS

At randomization, the median A1C was 7.3% (57 mmol/mol) for GLIPULIN and 7.4% (56.3 mmol/mol) for BBI, and glucose CVs were 30.3 for BBI and 31.9 for GLIPULIN. At 26 weeks, A1C levels were similar (7.1% [54 mmol/mol] vs. 7.2% [55 mmol/mol]), whereas mean CV improved with GLIPULIN (-2.4 vs. 0.4, P = 0.047). Other GV indices followed similar nonsignificant patterns of improvement with GLIPULIN. There were no differences in hypoglycemic events during CGM or arrhythmias during electrocardiographic monitoring. On-trial changes in body weight (-4.8 kg vs. +0.7 kg, P < 0.001), alanine aminotransferase (P = 0.0002), and serum amyloid A (P = 0.023) favored GLIPULIN.

CONCLUSIONS

GLIPULIN reduced GV, weight, and some cardiometabolic risk markers while maintaining equivalent A1C levels versus BBI and might improve clinical outcomes in a larger trial.

Continuous glucose monitoring in the subcutaneous tissue over a 14-day sensor wear period

BACKGROUND

Glucose monitoring systems using subcutaneously inserted sensors are currently labeled for up to 7 days of wear. In this study, we evaluated the feasibility of a 14-day wear duration using a modified version of the sensor found in the Freestyle Navigator™ continuous glucose monitoring system.

METHODS

Sixty-two subjects with diabetes were enrolled in the study. One sensor per subject was inserted on the arm for a wear time of 14 days. Two different calibration algorithms were applied retrospectively, one that uses periodic sensor recalibrations and one without recalibrations. Sensor in vivo stability was determined by least square regression analysis using capillary blood glucose. Mean absolute relative difference (MARD) and mean relative difference were calculated. Consensus error grid analysis was performed by day and over the 14-day wear period to evaluate accuracy of both systems. The sensor insertion sites were inspected after sensor removal for skin reactions.

RESULTS

Sensor data from 55 subjects were used for the analysis. The accuracy metrics for the system with recalibration were calculated to MARD = 13.9% and 84.0% in zone A (error grid analysis). The system without recalibration performed significantly better, resulting in MARD of 12.2% and 88.0% in zone A (p < .0001). The maximum change of in vivo sensor sensitivity over the 14-day wear period was 2% per day. Two subjects reported pain during the first 5 days of sensor wear, and 1 subject reported itching at the sensor site. No further skin reactions were noticed.

CONCLUSIONS

The study shows that a 14-day sensor wear period is achievable. Moreover, sensors using "wired enzyme" technology showed excellent in vivo stability, with no significant sensitivity loss over the 14-day wear period.

Continuous glucose monitoring: evidence and consensus statement for clinical use

Continuous glucose monitoring (CGM) is an essential tool for modern diabetes therapy. Randomized controlled studies have provided evidence that hemoglobin A1c (HbA1c) results can be improved in patients with type 1 diabetes with elevated baseline HbA1c when using CGM frequently enough and that the frequency and duration of hypoglycemic events can be reduced in patients with satisfactory baseline HbA1c. The CGM group within the Working Group Diabetes Technology (AGDT) of the German Diabetes Association (DDG) has defined evidence-based indications for the practical use of CGM in this consensus statement related to hypoglycemia (frequent, severe, or nocturnal) or hypoglycemia unawareness, insufficient metabolic control despite use of all possible therapeutic options and patient compliance, pregnancy associated with inadequate blood glucose results, and the need for more than 10 blood glucose measurements per day. Contraindications and defined preconditions for the successful use of CGM should be considered.

Is the response of continuous glucose monitors to physiological changes in blood glucose levels affected by sensor life?

BACKGROUND

None of the studies concerned with the performance of a continuous glucose monitor (CGM) over time has examined the extent to which extended periods of wear affect the responses of both CGM accuracy and lag time to rapid changes in blood glucose levels. Here we propose a novel approach to address these issues.

METHODS

Eight participants without diabetes were each fitted with two CGMs (Paradigm(®) 722 Real-Time [Medtronic, Northridge, CA]; abdominal and triceps regions) and completed fasted oral glucose challenges (OGCs) on six occasions over a 9-day period, while the CGMs were worn without removal. Arterialized blood samples were collected for comparison with CGM values.

RESULTS

There were marked mismatches and lag times between blood glucose and CGM values in response to all OGCs, most notably during the initial rapid increase in glucose levels. Abdominal and triceps CGMs consistently underestimated peak blood glucose by an average of 2.7±0.2 and 2.9±0.2 mM, respectively, and were associated with a peak blood glucose lag of 21.6±1.8 and 18.1±1.6 min, respectively. CGM accuracy did not deteriorate over 9 days of wear in OGCs for either the abdominal or triceps sensor. All participants found the triceps sensor site more comfortable than the abdominal site (P<0.05).

CONCLUSIONS

The current CGM sensor tested here may be used for extended periods, providing added economic benefits for the wearer. However, the marked inaccuracy and lag time of CGM readings when blood glucose levels change rapidly within the physiological range must be considered for optimal CGM use in glycemic management.

Real-time glucose estimation algorithm for continuous glucose monitoring using autoregressive models

BACKGROUND

Continuous glucose monitors (CGMs) present a problem of lack of accuracy, especially in the lower range, sometimes leading to missed or false hypoglycemia. A new algorithm is presented here aimed at improving the measurement accuracy and hypoglycemia detection. Its core is the estimation of blood glucose (BG) in real time (RT) from CGM intensity readings using autoregressive (AR) models.

METHODS

Eighteen patients with type 1 diabetes were monitored for three days (one at the hospital and two at home) using the CGMS Gold. For these patients, BG samples were taken every 15 min for 2 h after meals and every half hour otherwise during the first day. The relationship between the current measured by the CGMS Gold and BG was learned by an AR model, allowing its RT estimation. New capillary glucose measurements were used to correct the model BG estimations.

RESULTS

A total of 563 paired points were obtained from BG and monitor readings to validate the new algorithm. 98.5% of paired points fell in zones A+B of the Clarke error grid analysis with the proposed algorithm. The overall mean and median relative absolute differences (RADs) were 9.6% and 6.7%. Measurements meeting International Organization for Standardization (ISO) criteria were 88.7%. In the hypoglycemic range, the mean and median RADs were 8.1% and 6.0%, and measurements meeting ISO criteria were 86.7%. The sensitivity and specificity with respect to hypoglycemia detection were 91.5% and 95.0%.

CONCLUSIONS

The performance measured with both clinical and numerical accuracy metrics illustrates the improved accuracy of the proposed algorithm compared with values presented in the literature. A significant improvement in hypoglycemia detection was also observed.

Clinical review: Realistic expectations and practical use of continuous glucose monitoring for the endocrinologist

CONTEXT

Real-time continuous glucose monitoring (CGM) has been available for type 1 diabetes for several years. This paper is a status report on our early experiences with this next technology.

EVIDENCE ACQUISITION

The two major sources of data acquisition included PubMed search strategies and personal experience of the author from clinical experience.

EVIDENCE SYNTHESIS

Data assessing CGM accuracy, short-term outcomes (12 wk), and longer term outcomes (6 months) are reported. Potential strategies for successful and efficient use in an office or clinic setting are also discussed. Practical aspects of CGM use (alarm settings, using glycemic trending information) are also reviewed.

CONCLUSIONS

Accuracy of this technology has improved in the short amount of time it has been available. Six-month data suggest that patient selection is a key for success. Patients who do not understand or practice the basics of intensive insulin therapy have the greatest challenges. Those who do best watch the receiver frequently, continue with frequent home blood glucose monitoring, use the trending information to make insulin adjustments, and understand the limitations of the technology. With insurance reimbursement improving, CGM is gaining acceptance as an important tool for the management of type 1 diabetes. Like home blood glucose monitoring and insulin pump therapy, this technology by itself is not a panacea for diabetes control. However, it further adds to our ability to improve the lives of people with diabetes. Long-term, the hope is that this technology will pave the way for a "closed-loop" device.

Clinical experience with continuous glucose monitoring in adults

Despite recent advances in therapy, achieving adequate glycemic control may be difficult for a large number of patients with diabetes. Real-time (RT)-continuous glucose monitoring (CGM) has the potential to improve glycemic control through immediate feedback to the properly trained patient. However, limitations exist both in interpreting the results of published randomized clinical trials on CGM use and in extrapolating the results to the diabetes population at large. This review summarizes the evidence for use, identifies suitable candidates, describes optimal implementation, and employs case scenarios in order to emphasize practical aspects of RT-CGM use in adults. Establishment of expectations and comprehensive education in intensive insulin therapy and RT-CGM use are necessary for successful implementation. Because the technology has been shown to be most useful in patients who are actively viewing and responding to RT data, patients should receive explicit instructions for active self-adjustment of insulin and lifestyle elements. While the technology is improving, false alarms remain a significant barrier to optimal use. The utility of RT-CGM for patients with severe hypoglycemia or hypoglycemia unawareness has not been established. Finally, studies are needed to determine the sustainability of improvements in glycemic control, as well as cost-effectiveness and practicality of implementation into busy real-world practice.