Current application of continuous glucose monitoring in the treatment of diabetes: pros and cons

Blood glucose concentration prediction based on VMD-KELM-AdaBoost

The time series of blood glucose concentration in diabetic patients are time-varying, nonlinear, and non-stationary. In order to improve the accuracy of blood glucose prediction, a multi-scale combination short-term blood glucose prediction model was constructed by combining the variational mode decomposition (VMD) method, the kernel extreme learning machine (KELM), and the AdaBoost algorithm (VMD-ELM-AdaBoost). Firstly, the blood glucose concentration series were decomposed into a set of intrinsic modal functions (IMFs) with different scales by the VMD method. On this basis, the KELM neural network and AdaBoost algorithm are combined to predict each IMF component. Finally, the cumulative blood glucose concentration prediction value is obtained by accumulating the KELM-AdaBoost prediction results of each IMF. The time series of measured blood glucose concentration were used for experimental analysis; the experimental results show that the proposed VMD-KELM-AdaBoost method has higher prediction accuracy compared with the classical prediction models such as ELM, KELM, SVM, and LSTM. The proposed VMD-KELM-AdaBoost model can still achieve high prediction accuracy 60 min in advance (the mean values of RMSE, MAPE, and CC are about 10.1422, 4.8629%, and 0.8737 respectively); in Clarke error mesh analysis, the proportion of falling into A region is about 95.7%; the sensitivity and false alarm rate of early alarm of hypoglycemia were 94.8% and 7.7%, respectively. Graphical abstract We have proposed a new prediction model. In the first part, for reducing thenon-stationarity, the data of blood glucose concentration was decomposed as a series ofIMF by VMD. In the second part, a prediction model based KELM and Adaboost wasestablished. In the third part, the KELM-Adaboost model was used to predict each IMF,and the predicted values of all IMFS were superimposed to obtain the final predictionresult of blood glucose concentration.

Barriers to Continuous Glucose Monitoring in People With Type 1 Diabetes: Clinician Perspectives

The purpose of this study was to determine clinician attitudes about the distinct barriers to uptake of continuous glucose monitoring (CGM) among people with diabetes. Survey data were collected measuring individual barriers, prerequisites to CGM, confidence in addressing barriers, and clinic staff resources. Results show that clinicians commonly report barriers to using CGM among people with diabetes in their clinic. Furthermore, clinicians who report a high number of barriers do not feel confident in overcoming the barriers to CGM. Interventions that attempt to empower clinicians to address concerns about CGM among people with diabetes may be warranted because low uptake does not appear to be directly related to available resources or prerequisites to starting CGM.

Using Cluster Analysis to Understand Clinician Readiness to Promote Continuous Glucose Monitoring Adoption

BACKGROUND

Many people with type 1 diabetes (T1D) report barriers to using continuous glucose monitoring (CGM). Diabetes care providers may have their own barriers to promoting CGM uptake. The goal of this study was to develop clinician "personas" with regard to readiness to promote CGM uptake.

METHODS

Diabetes care providers who treat people with T1D (N = 209) completed a survey on perceived patient barriers to device uptake, technology attitudes, and characteristics and barriers specific to their clinical practice. K-means cluster analyses grouped the sample by CGM barriers and attitudes. ANOVAs and chi-square tests assessed group differences on provider and patient characteristics. The authors assigned descriptive names for each persona.

RESULTS

Analyses yielded three clinician personas regarding readiness to promote CGM uptake. Ready clinicians (20% of sample; 24% physicians, 38% certified diabetes educators/CDEs) had positive technology attitudes, had clinic time to work with patients using CGM, and found it easy to keep up with technology advances. In comparison, Cautious clinicians (41% of sample; 17% physicians, 53% CDEs) perceived that their patients had many barriers to adopting CGM and had less time than the Ready group to work with patients using CGM data. Not Yet Ready clinicians (40% of sample; 9% physicians; 79% CDEs) had negative technology attitudes and the least clinic time to work with CGM data. They found it difficult to keep up with technology advances.

CONCLUSION

Some diabetes clinicians may benefit from tailored interventions and additional time and resources to empower them to help facilitate increased uptake of CGM technology.

Effects of breaking up sitting on adolescents' postprandial glucose after consuming meals varying in energy: a cross-over randomised trial

OBJECTIVES

To explore the impact of uninterrupted sitting versus sitting with resistance-type activity breaks on adolescents' postprandial glucose responses while consuming a diet varying in energy.

DESIGN

Cross-over randomised trial.

METHODS

Thirteen healthy participants (16.4±1.3years) completed a four-treatment cross-over trial: (1) uninterrupted sitting+high-energy diet; (2) sitting with breaks+high-energy diet; (3) uninterrupted sitting+standard-energy diet; and (4) sitting with breaks+standard-energy diet. For all four conditions, two identical meals were consumed; at 0h and 3h. A continuous glucose monitoring system (CGM) recorded interstitial glucose concentrations every five minutes. Linear mixed models examined differences in glucose positive incremental area under the curve (iAUC) and total AUC between the sitting and diet conditions for the first meal, second meal and entire trial period.

RESULTS

Compared to the uninterrupted sitting conditions, the breaks condition elicited a 36.0mmol/L/h (95%CI 6.6-65.5) and 35.9mmol/L/h (95%CI 6.6-65.5) lower iAUC response after the first and second meal, respectively, but not for the entire trial period or for total AUC. Compared to the standard-energy diet, the high-energy diet elicited a 55.0mmol/L/h (95%CI 25.8-84.2) and 75.7mmol/L/h (95%CI 8.6-142.7) higher iAUC response after the first meal and entire trial, respectively. Similar response to the high-energy diet were observed for total AUC.

CONCLUSIONS

According to iAUC, interrupting sitting had a significant effect on lowering postprandial glucose for both dietary conditions, however, it was not significant when examining total AUC. Larger studies are needed to confirm these findings.

CLINICAL TRIAL REGISTRATION NUMBER

ACTRN12615001145594.

Optimal Use of Diabetes Devices: Clinician Perspectives on Barriers and Adherence to Device Use

BACKGROUND

Insulin pumps and continuous glucose monitors (CGM) can improve glycemic control for individuals with type 1 diabetes (T1D). Device uptake rates continue to show room for improvement, and consistent adherence is needed to achieve better outcomes. Diabetes health care providers have important roles to play in promoting device use and adherence.

METHODS

We surveyed 209 clinicians who treat people with type 1 diabetes to examine perceptions of barriers to device uptake, attitudes toward diabetes technology, and resources needed for clinicians to improve device uptake. We compared findings with our survey of adults with T1D.

RESULTS

Younger clinicians treated more patients using insulin pumps ( r = -.26, P < .001) and CGM ( r = -.14, P = .02), and had more positive attitudes about diabetes technology ( r = -.23, P = .001). The most frequently endorsed modifiable barriers were perceptions that patients dislike having the device on their body (73% pump; 63% CGM), dislike the alarms (61% CGM), and do not understand what to do with device information or features (40% pump; 46% CGM). Clinicians wanted lower cost and better insurance coverage for their patients, and they recommended counseling and education to help address barriers and improve adherence to devices.

CONCLUSION

Clinicians perceive many barriers to their patients initiating and adhering to diabetes devices. Findings highlight opportunities for intervention to improve clinician-patient communication around device barriers to help address them.

Treatment of reactive hypoglycemia with the macrobiotic Ma-pi 2 diet as assessed by continuous glucose monitoring: The MAHYP randomized crossover trial

BACKGROUND AND AIMS

Nutritional therapy is recommended for management of reactive hypoglycemia (RH), a condition characterized by hypoglycemia that occurs within four hours after a meal. The macrobiotic Ma-Pi 2 diet improves glycemic control in subjects with type 2 diabetes. We explored the effect of this diet on outcomes in non-diabetic individuals with RH.

MATERIALS AND METHODS

Twelve subjects with RH were randomized to the Ma-Pi 2 diet for three days and a control diet for three days in a randomized crossover design. Subjects received snacks on two days out of each three-day period only, and were monitored using continuous glucose monitoring. The 24-h period was divided into daytime (08:00-22:30h [subdivided into 'daytime without snacks' and 'daytime with snacks']) and night-time (22:31-07:59h). The effects of the two diets on the number of RH events (blood glucose <70mg/dL [3.9mmol/L]) and the percentage distribution of glucose readings within each of 16 glycemic intervals from <40mg/dL (2.2mmol/L) to >180mg/dL (4.4mmol/L) were determined.

RESULTS

There were significantly fewer RH events on the Ma-Pi 2 diet than the control diet during daytime without snacks (-2.5 events; 95% CI: -7.5, 0.0; P=0.022) and daytime with snacks (-4.25 events; 95% CI: -7.5; -2.0; P=0.013) but no difference at night. The percentage of glucose readings in the interval 71-80mg/dL (3.9-4.4mmol/L) was significantly higher on the control diet during daytime with and without snacks (P=0.03 for both), while the percentage of glucose readings in the interval 91-100mg/dL (5.1-5.6mmol/L) was significantly higher on the Ma-Pi 2 diet during daytime without snacks (P=0.02).

CONCLUSIONS

The macrobiotic Ma-Pi 2 diet reduced blood glucose excursions during the day, thereby facilitating glycemic control in subjects with RH. The Ma-Pi 2 diet represents an effective nutritional tool for management of RH.

Diabetes Device Use in Adults With Type 1 Diabetes: Barriers to Uptake and Potential Intervention Targets

OBJECTIVE

Diabetes devices (insulin pumps, continuous glucose monitors [CGMs]) are associated with benefits for glycemic control, yet uptake of these devices continues to be low. Some barriers to device uptake may be modifiable through psychosocial intervention, but little is known about which barriers and which patients to target.

RESEARCH DESIGN AND METHODS

We surveyed 1,503 adult T1D Exchange participants (mean age 35.3 [SD 14.8] years, mean diagnosis duration 20.4 [SD 12.5] years) to investigate barriers to device uptake, understand profiles of device users versus nonusers, and explore differences by age and sex. Scales used were the Diabetes Distress Scale, Technology Use Attitudes (General and Diabetes-Specific), and Barriers to Device Use and Reasons for Discontinuing Devices.

RESULTS

Most commonly endorsed modifiable barriers were related to the hassle of wearing devices (47%) and disliking devices on one's body (35%). CGM users (37%) were older than nonusers (mean 38.3 vs. 33.5 years), had diabetes for longer (22.9 vs. 18.8 years), had more positive technology attitudes (22.6-26.0 vs. 21.4-24.8), and reported fewer barriers to using diabetes technology than nonusers (3.3 vs. 4.3). The youngest age-group (18-25 years) had the lowest CGM (26% vs. 40-48%) and insulin pump (64% vs. 69-77%) uptake, highest diabetes distress (2.2 vs. 1.8-2.1), and highest HbA_1c levels (8.3% [67 mmol/mol] vs. 7.2-7.4% [55-57 mmol/mol]).

CONCLUSIONS

Efforts to increase device use need to target physical barriers to wearing devices. Because young adults had the lowest device uptake rates, highest distress, and highest HbA_1c compared with older age-groups, they should be the focus of future interventions to increase device use.

A new horizon for glucose monitoring

Regular self-monitoring of blood glucose is crucial for proper insulin dosing and gives a reliable foundation for reasonable glycaemic control. According to recent data, recommended values for glycated haemoglobin A1c as set by the professional associations remain out of the reach for a large proportion of the paediatric population. In the last decades, the treatment of type 1 diabetes has changed significantly as new devices gain a role in routine clinical care. Real-time glucose levels can be monitored with continuous glucose monitoring (CGM), which provides a broad spectrum of information on glucose trends on a moment-to-moment basis. This information can be useful for patients' decision making and clinicians' understanding of patients' conduct. However, several barriers, including the current price, impede a broader use of CGM in most regions of the world. This review summarizes data from randomized, controlled trials that included a paediatric population, and it provides some evidence-based visions for the possible broader utilization of CGM, also for incorporation into insulin delivery devices that enable a closed-loop insulin delivery.

Are Systematic Reviews and Meta-Analyses Appropriate Tools for Assessing Evolving Medical Device Technologies?

Systematic reviews and meta-analyses (SRMAs) provide unique insights into comparative effectiveness of diabetes treatments. However, use of these analyses may be inappropriate for assessing the value and utility of technologies that involve significant behavioral interventions and encompass rapidly evolving technologies such as real-time continuous glucose monitoring (RT-CGM). The rapid evolution of RT-CGM, compared with the time required for publication of clinical studies used in SRMAs, may preclude differentiation between past and current generations of devices. In addition, the effect of performance and usability differences between the various commercial devices on possible clinical outcomes associated with the devices are often not clearly discussed, and many of the RT-CGM studies assessed in SRMAs do not provide adequate information regarding whether and/or to what degree study subjects and clinicians were trained to use the RT-CGM and utilize the data to adjust therapy. Although numerous clinical studies have shown that the glycemic benefit of RT-CGM is related to the frequency and duration of use, a disproportionate number of RT-CGM studies included in recent SRMAs are based on the results of the intention-to-treat analyses and do not consider this fundamental behavioral component in their conclusions. Given these limitations, the generalizability of SRMA conclusions may be limited, and findings from these reports may significantly underestimate the potential glycemic benefit of current and future devices, posing challenges for coverage and reimbursement. We reviewed the potential limitations of the recent Cochrane Collaboration report on CGM, focusing on the 12 studies that assessed RT-CGM use in adults, children/adolescents or both.

Preclinical Evaluation of Poly(HEMA-co-acrylamide) Hydrogels Encapsulating Glucose Oxidase and Palladium Benzoporphyrin as Fully Implantable Glucose Sensors

BACKGROUND

Continuous glucose monitors (CGMs) require percutaneous wire probes to monitor glucose. Sensors based on luminescent hydrogels are being explored as fully implantable alternatives to traditional CGMs. Our previous work investigated hydrogel matrices functionalized with enzymes and oxygen-quenched phosphors, demonstrating sensitivity to glucose, range of response, and biofouling strongly depend on the matrix material. Here, we further investigate the effect of matrix composition on overall performance in vitro and in vivo.

METHODS

Sensors based on three hydrogels, a poly(2-hydroxyethyl methacrylate) (pHEMA) homopolymer and 2 poly(2-hydroxyethyl methacrylate-co-acrylamide) (pHEMA-co-AAm) copolymers, were compared. These were used to entrap glucose oxidase (GOx), catalase, and an oxygen-sensitive benzoporphyrin phosphor. All sensor formulations were evaluated for glucose response and stability at physiological temperatures. Selected sensors were then evaluated as implanted sensors in a porcine model challenged with glucose and insulin. The animal protocol used in this study was approved by an IACUC committee at Texas A&M University.

RESULTS

PHEMA-co-AAm copolymer hydrogels (75:25 HEMA:AAm) yielded the most even GOx and dye dispersion throughout the hydrogel matrix and best preserved GOx apparent activity. In response to in vitro glucose challenges, this formulation exhibited a dynamic range of 12-167 mg/dL, a sensitivity of 1.44 ± 0.46 µs/(mg/dL), and tracked closely with reference capillary blood glucose values in vivo.

CONCLUSIONS

The hydrogel-based sensors exhibited excellent sensitivity and sufficiently rapid response to the glucose levels achieved in vivo, proving feasibility of these materials for use in real-time glucose tracking. Extending the dynamic range and assessing long-term effects in vivo are ongoing efforts.

Clinical accuracy of a continuous glucose monitoring system with an advanced algorithm

We assessed the performance of a modified Dexcom G4 Platinum system with an advanced algorithm, in comparison with frequent venous samples measured on a laboratory reference (YSI) during a clinic session and in comparison to self-monitored blood glucose (SMBG) during home use. Fifty-one subjects with diabetes were enrolled in a prospective multicenter study. Subjects wore 1 sensor for 7-day use and participated in one 12-hour in-clinic session on day 1, 4, or 7 to collect YSI reference venous glucose every 15 minutes and capillary SMBG test every 30 minutes. Carbohydrate consumption and insulin dosing and timing were manipulated to obtain data in low and high glucose ranges. In comparison with the laboratory reference method (n = 2,263) the system provided a mean and median absolute relative differences (ARD) of 9.0% and 7.0%, respectively. The mean absolute difference for CGM was 6.4 mg/dL when the YSIs were within hypoglycemia ranges (≤ 70 mg/dL). The percentage in the clinically accurate Clarke error grid A zone was 92.4% and in the benign error B zone was 7.1%. Majority of the sensors (73%) had an aggregated MARD in reference to YSI ≤ 10%. The MARD of CGM-SMBG for home use was 11.3%. The study showed that the point and rate accuracy, clinical accuracy, reliability, and consistency over the duration of wear and across glycemic ranges were superior to current commercial real-time CGM systems. The performance of this CGM is reaching that of a self-monitoring blood glucose meter in real use environment.

Practical approaches for self-monitoring of blood glucose: an Asia-Pacific perspective

Comprehensive glycemic control is necessary to improve outcomes and avoid complications in individuals with diabetes. Self-monitoring of blood glucose (SMBG) is a key enabler of glycemic assessment, providing real-time information that complements HbA1c monitoring and supports treatment optimization. However, SMBG is under-utilized by patients and physicians within the Asia-Pacific region, because of barriers such as the cost of monitoring supplies, lack of diabetes self-management skills, or concerns about the reliability of blood glucose readings. Practice recommendations in international and regional guidelines vary widely, and may not be detailed or specific enough to guide SMBG use effectively. This contributes to uncertainty among patients and physicians about how best to utilize this tool: when and how often to test, and what action(s) to take in response to high or low readings. In developing a practical SMBG regimen, the first step is to determine the recommended SMBG frequency and intensity needed to support the chosen treatment regimen. If there are practical obstacles to monitoring, such as affordability or access, physicians should identify the most important aspects of glycemic control to target for individual patients, and modify monitoring patterns accordingly. This consensus paper proposes a selection of structured, flexible SMBG patterns that can be tailored to the clinical, educational, behavioral, and financial requirements of individuals with diabetes.

High reported treatment satisfaction in people with type 1 diabetes switching to latest generation insulin pump regardless of previous therapy

The effects of transition by individuals with type 1 diabetes (T1D) to more recently available continuous glucose monitoring (CGM)-enabled insulin pumps from either multiple daily insulin injections (MDI) or older insulin pumps on treatment satisfaction have not been well studied. We conducted a survey to assess treatment satisfaction among users of the Animas(®) Vibe™ insulin pump, a latest generation insulin pump (LGIP) system (CGM-enabled), after switching from MDI or earlier generation insulin pumps. Individuals with T1D from 141 centers in 5 countries and 4 language areas participated in the survey. Treatment satisfaction was assessed by the Insulin Treatment Satisfaction Questionnaire (ITSQ), which was included in a 50-item online questionnaire that also assessed preference for using the LGIP compared with previous treatment and satisfaction with key LGIP features. A total of 356 individuals, ages 12-79 years, responded to the survey: mean (SD) age 38.4 (16.1) years; diabetes duration 19.1 (13.3) years; female 59%; previously treated with MDI 58%. Overall mean (SD) ITSQ scores were high among all respondents regardless of prior treatment: 95.1 (23.2) (scale: 0-132). No differences between previous-treatment groups were seen. Most (83%) of respondents rated the LGIP to be better than their previous insulin delivery system: "much better" (65%), "a bit better" (18%) regardless of age, and 95% would recommend using the LGIP to others. Use of the Animas Vibe was associated with high treatment satisfaction and perceived as a better method of insulin delivery regardless of previous insulin therapy or age.

Glucose excursions and glycaemic control during Ramadan fasting in diabetic patients: insights from continuous glucose monitoring (CGM)

AIM

Ramadan fasting represents a major shift in meal timing and content for practicing Muslims. This study used continuous glucose monitoring (CGM) to assess changes in markers of glycaemic excursions during Ramadan fasting to investigate the short-term safety of this practice in different groups of patients with diabetes.

METHODS

A total of 63 subjects (56 with diabetes, seven healthy volunteers; 39 male, 24 female) had CGM performed during, before and after Ramadan fasting. Mean CGM curves were constructed for each group for these periods that were then used to calculate indicators of glucose control and excursions. Post hoc data analyses included comparisons of different medication categories (metformin/no medication, gliptin, sulphonylurea and insulin). Medication changes during Ramadan followed American Diabetes Association guidelines.

RESULT

Among patients with diabetes, there was a significant difference in mean CGM curve during Ramadan, with a slow fall during fasting hours followed by a rapid rise in glucose level after the sunset meal (iftar). The magnitude of this excursion was greatest in the insulin-treated group, followed by the sulphonylurea-treated group. Markers of control deteriorated in a small number (n=3) of patients. Overall, whether fasting or non-fasting, subjects showed no statistically significant changes in mean interstitial glucose (IG), mean amplitude of glycaemic excursion (MAGE), high and low blood glucose indices (HBGI/LBGI), and number of glucose excursions and rate of hypoglycaemia.

CONCLUSION

The main change in glycaemic control with Ramadan fasting in patients with diabetes is in the pattern of excursions. Ramadan fasting caused neither overall deterioration nor improvement in the majority of patients with good baseline glucose control.

Multiple-Input Subject-Specific Modeling of Plasma Glucose Concentration for Feedforward Control

The ability to accurately develop subject-specific, input causation models, for blood glucose concentration (BGC) for large input sets can have a significant impact on tightening control for insulin dependent diabetes. More specifically, for Type 1 diabetics (T1Ds), it can lead to an effective artificial pancreas (i.e., an automatic control system that delivers exogenous insulin) under extreme changes in critical disturbances. These disturbances include food consumption, activity variations, and physiological stress changes. Thus, this paper presents a free-living, outpatient, multiple-input, modeling method for BGC with strong causation attributes that is stable and guards against overfitting to provide an effective modeling approach for feedforward control (FFC). This approach is a Wiener block-oriented methodology, which has unique attributes for meeting critical requirements for effective, long-term, FFC.

Design, development, and evaluation of a novel microneedle array-based continuous glucose monitor

The development of accurate, minimally invasive continuous glucose monitoring (CGM) devices has been the subject of much work by several groups, as it is believed that a less invasive and more user-friendly device will result in greater adoption of CGM by persons with insulin-dependent diabetes. This article presents the results of preliminary clinical studies in subjects with diabetes of a novel prototype microneedle-based continuous glucose monitor. In this device, an array of tiny hollow microneedles is applied into the epidermis from where glucose in interstitial fluid (ISF) is transported via passive diffusion to an amperometric glucose sensor external to the body. Comparison of 1396 paired device glucose measurements and fingerstick blood glucose readings for up to 72-hour wear in 10 diabetic subjects shows the device to be accurate and well tolerated by the subjects. Overall mean absolute relative difference (MARD) is 15% with 98.4% of paired points in the A+B region of the Clarke error grid. The prototype device has demonstrated clinically accurate glucose readings over 72 hours, the first time a microneedle-based device has achieved such performance.

A new-generation continuous glucose monitoring system: improved accuracy and reliability compared with a previous-generation system

BACKGROUND

Use of continuous glucose monitoring (CGM) systems can improve glycemic control, but widespread adoption of CGM utilization has been limited, in part because of real and perceived problems with accuracy and reliability. This study compared accuracy and performance metrics for a new-generation CGM system with those of a previous-generation device.

SUBJECTS AND METHODS

Subjects were enrolled in a 7-day, open-label, multicenter pivotal study. Sensor readings were compared with venous YSI measurements (blood glucose analyzer from YSI Inc., Yellow Springs, OH) every 15 min (±5 min) during in-clinic visits. The aggregate and individual sensor accuracy and reliability of a new CGM system, the Dexcom(®) (San Diego, CA) G4™ PLATINUM (DG4P), were compared with those of the previous CGM system, the Dexcom SEVEN(®) PLUS (DSP).

RESULTS

Both study design and subject characteristics were similar. The aggregate mean absolute relative difference (MARD) for DG4P was 13% compared with 16% for DSP (P<0.0001), and 82% of DG4P readings were within ± 20 mg/dL (for YSI ≤ 80 mg/dL) or 20% of YSI values (for YSI >80 mg/dL) compared with 76% for DSP (P<0.001). Ninety percent of the DG4P sensors had an individual MARD ≤ 20% compared with only 76% of DSP sensors (P=0.015). Half of DG4P sensors had a MARD less than 12.5% compared with 14% for the DSP sensors (P=0.028). The mean absolute difference for biochemical hypoglycemia (YSI <70 mg/dL) for DG4P was 11 mg/dL compared with 16 mg/dL for DSP (P<0.001).

CONCLUSIONS

The performance of DG4P was significantly improved compared with that of DSP, which may increase routine clinical use of CGM and improve patient outcomes.

Evaluation of the performance of a novel system for continuous glucose monitoring

BACKGROUND

The performance of a continuous glucose monitoring (CGM) system in the early stage of development was assessed in an inpatient setting that simulates daily life conditions of people with diabetes. Performance was evaluated at low glycemic, euglycemic, and high glycemic ranges as well as during phases with rapid glucose excursions.

METHODS

Each of the 30 participants with type 1 diabetes (15 female, age 47 ± 12 years, hemoglobin A1c 7.7% ± 1.3%) wore two sensors of the prototype system in parallel for 7 days. Capillary blood samples were measured at least 16 times per day (at least 15 times per daytime and at least once per night). On two subsequent study days, glucose excursions were induced. For performance evaluation, the mean absolute relative difference (MARD) between CGM readings and paired capillary blood glucose readings and precision absolute relative difference (PARD), i.e., differences between paired CGM readings were calculated.

RESULTS

Overall aggregated MARD was 9.2% and overall aggregated PARD was 7.5%. During induced glucose excursions, MARD was 10.9% and PARD was 7.8%. Lowest MARD (8.5%) and lowest PARD (6.4%) were observed in the high glycemic range (euglycemic range, MARD 9.1% and PARD 7.4%; low glycemic range, MARD 12.3% and PARD 12.4%).

CONCLUSIONS

The performance of this prototype CGM system was, particularly in the hypoglycemic range and during phases with rapid glucose fluctuations, better than performance data reported for other commercially available systems. In addition, performance of this prototype sensor was noticeably constant over the whole study period. This prototype system is not yet approved, and performance of this CGM system needs to be further assessed in clinical studies.

Overview of a novel sensor for continuous glucose monitoring

The core element of a continuous glucose monitoring (CGM) system is the glucose sensor, which should enable reliable CGM readings in the interstitial fluid in subcutaneous tissue for a period of several days. The aim of this article is to describe the layout and constituents of a novel glucose sensor and the rationale behind the measures that were used to optimize its performance. In order to achieve a stable glucose sensor signal, special attention was paid to the sensor materials and architecture, i.e., biocompatible coating of the sensor, limitation of glucose flux into the working electrode, low oxidation potential by use of manganese dioxide, and a tissue-averaging sensor design. A series of in vitro and in vivo evaluations showed that the sensor enables stable and accurate glucose sensing in the subcutaneous tissue for up to 7 days. Parallel measurements with four sensors in a single patient showed a close agreement between these sensors. In summary, this high-performance needle-type glucose sensor is well suited for CGM in patients with diabetes.

Substrate specificity and interferences of a direct-electron-transfer-based glucose biosensor

OBJECTIVE

Electrochemical sensors for glucose monitoring employ different signal transduction strategies for electron transfer from the biorecognition element to the electrode surface. We present a biosensor that employs direct electron transfer and evaluate its response to various interfering substances known to affect glucose biosensors.

METHODS

The enzyme cellobiose dehydrogenase (CDH) was adsorbed on the surface of a carbon working electrode and covalently bound by cross linking. The response of CDH-modified electrodes to glucose and possible interfering compounds was measured by flow-injection analysis, linear sweep, and chronoamperometry.

RESULTS

Chronoamperometry showed initial swelling/wetting of the electrode. After stabilization, the signal was stable and a sensitivity of 0.21 µA mM-1 cm-2 was obtained. To investigate the influence of the interfering substances on the biorecognition element, the simplest possible sensor architecture was used. The biosensor showed little (<5% signal deviation) or no response to various reported electroactive or otherwise interfering substances.

CONCLUSIONS

Direct electron transfer from the biorecognition element to the electrode is a new principle applied to glucose biosensors, which can be operated at a low polarization potential of -100 mV versus silver/silver chloride. The reduction of interferences by electrochemically active substances is an attractive feature of this promising technology for the development of continuous glucose biosensors.

A MEMS differential viscometric sensor for affinity glucose detection in continuous glucose monitoring

Micromachined viscometric affinity glucose sensors have been previously demonstrated using vibrational cantilever and diaphragm. These devices featured a single glucose detection module that determines glucose concentrations through viscosity changes of glucose-sensitive polymer solutions. However, fluctuations in temperature and other environmental parameters might potentially affect the stability and reliability of these devices, creating complexity in their applications in subcutaneously implanted continuous glucose monitoring (CGM). To address these issues, we present a MEMS differential sensor that can effectively reject environmental disturbances while allowing accurate glucose detection. The sensor consists of two magnetically driven vibrating diaphragms situated inside microchambers filled with a boronic-acid based glucose-sensing solution and a reference solution insensitive to glucose. Glucose concentrations can be accurately determined by characteristics of the diaphragm vibration through differential capacitive detection. Our in-vitro and preliminary in-vivo experimental data demonstrate the potential of this sensor for highly stable subcutaneous CGM applications.

1,5-Anhydroglucitol as a marker of maternal glycaemic control and predictor of neonatal birthweight in pregnancies complicated by type 1 diabetes mellitus

AIMS/HYPOTHESIS

Most pregnant women with type 1 diabetes mellitus achieve HbA1c targets; however, macrosomia remains prevalent and better pregnancy glycaemic markers are therefore needed. 1,5-Anhydroglucitol (1,5-AG) is a short-term marker of glycaemia, reflecting a period of 1 to 2 weeks. Its excretion rate depends on the renal glucose threshold and thus it is unclear whether it may be used in pregnant type 1 diabetes women. We evaluated 1,5-AG as a glycaemic marker and birthweight predictor in pregnant women with type 1 diabetes, and compared its performance with HbA1c.

METHODS

1,5-AG and HbA1c were measured in 82 pregnant women with type 1 diabetes. In addition, 58 continuous glucose monitoring system (CGMS) records were available. Macrosomia was defined as birthweight >90th centile. The data were analysed with Pearson's correlations, and linear and logistic regression models. Receiver operating characteristic (ROC) analysis was used to evaluate third trimester 1,5-AG as a predictor of macrosomia.

RESULTS

Unlike HbA1c, 1,5-AG strongly correlated with CGMS indices: the AUC above 7.8 mmol/l (r = -0.66; p < 0.001), average maximum glucose (r = -0.58; p < 0.001) and mean glucose (r = -0.54; p < 0.001). In the third trimester, 1,5-AG was the strongest predictor of macrosomia, with ROC AUC 0.81 (95% CI 0.70, 0.89). In contrast, HbA1c in the third trimester had a ROC AUC of 0.69 (95% CI 0.58, 0.81). The best discrimination was achieved when both markers were used jointly, yielding a ROC AUC of 0.84 (95% CI 0.76, 0.93).

CONCLUSIONS/INTERPRETATION

In pregnant women with type 1 diabetes, 1,5-AG is a better glycaemic marker than HbA1c, as assessed by CGMS. A decreased third trimester 1,5-AG level, either singly or with HbA1c, is a strong predictor of macrosomia.

Use of microneedle array devices for continuous glucose monitoring: a review

Microneedle array devices provide the opportunity to overcome the barrier characteristics of the outermost skin layer, the stratum corneum. This novel technology can be used as a therapeutic tool for transdermal drug delivery, including insulin, or as a diagnostic tool providing access to dermal biofluids, with subsequent analysis of its contents. Over the last decade, the use of microneedle array technology has been the focus of extensive research in the field of transdermal drug delivery. More recently, the diagnostic applications of microneedle technology have been developed. This review summarizes the existing evidence for the use of microneedle array technology as biosensors for continuous monitoring of the glucose content of interstitial fluid, focusing also on mechanics of insertion, microchannel characteristics, and safety profile.

Single-walled carbon nanotube-based near-infrared optical glucose sensors toward in vivo continuous glucose monitoring

This article reviews research efforts on developing single-walled carbon nanotube (SWNT)-based near-infrared (NIR) optical glucose sensors toward long-term in vivo continuous glucose monitoring (CGM). We first discuss the unique optical properties of SWNTs and compare SWNTs with traditional organic and nanoparticle fluorophores regarding in vivo glucose-sensing applications. We then present our development of SWNT-based glucose sensors that use glucose-binding proteins and boronic acids as a high-affinity molecular receptor for glucose and transduce binding events on the receptors to modulate SWNT fluorescence. Finally, we discuss opportunities and challenges in translating the emerging technology of SWNT-based NIR optical glucose sensors into in vivo CGM for practical clinical use.

Continuous subcutaneous insulin infusion for managing diabetes: women's health implications

The use of continuous subcutaneous insulin infusion (CSII), also called insulin pump therapy, is increasing for management of type 1 diabetes. This article provides a comprehensive background on CSII, reviews recent studies comparing it to multiple daily insulin injections, offers strategies to troubleshoot potential problems, and discusses the implications of CSII for women's health across the lifespan.

Short-term continuous glucose monitoring: effects on glucose and treatment satisfaction in patients with type 1 diabetes mellitus; a randomized controlled trial

Objective:  To assess whether 4 week's use of a continuous glucose monitoring (CGM) system improves glucose control, treatment satisfaction or health status, as compared to intensified conventional finger-prick measurements (ICFM) in patients with type 1 diabetes mellitus (DM1). Method:  Thirty patients suffering from DM1 for more than three years and treated with either insulin pumps or multiple daily insulin injections, were included in a randomised controlled cross-over trial. They were Caucasians of both genders, between 18 and 50 years, and had moderately well controlled diabetes. The participants performed either ICFM or CGM for 4 weeks, followed by an 8 week's observation period. Thereafter they were crossed over to the opposite intervention. HbA(1c) , hypoglycaemic episodes, treatment satisfaction and health status were assessed at all meetings, although HbA(1c) was the primary endpoint. Results:  At inclusion mean HbA(1c) was 7.8 ± 0.9 %. The mean change in HbA(1c) was -0.2 ± 0.1% and -0.2 ± 0.1% for the CGM and the ICFM periods, accordingly (p = 0.91). The mean changes in HbA(1c) during the combined treatment and observation periods were -0.1 ± 0.1% and -0.2 ± 0.1% for the CGM and the ICFM period, accordingly (p = 0.86). The frequency of severe hypoglycaemic episodes, treatment satisfaction and health status was also equal between the two interventions. No adverse events were observed.

Materials for diabetes therapeutics

This review is focused on the materials and methods used to fabricate closed-loop systems for type 1 diabetes therapy. Herein, we give a brief overview of current methods used for patient care and discuss two types of possible treatments and the materials used for these therapies-(i) artificial pancreases, comprised of insulin producing cells embedded in a polymeric biomaterial, and (ii) totally synthetic pancreases formulated by integrating continuous glucose monitors with controlled insulin release through degradable polymers and glucose-responsive polymer systems. Both the artificial and the completely synthetic pancreas have two major design requirements: the device must be both biocompatible and be permeable to small molecules and proteins, such as insulin. Several polymers and fabrication methods of artificial pancreases are discussed: microencapsulation, conformal coatings, and planar sheets. We also review the two components of a completely synthetic pancreas. Several types of glucose sensing systems (including materials used for electrochemical, optical, and chemical sensing platforms) are discussed, in addition to various polymer-based release systems (including ethylene-vinyl acetate, polyanhydrides, and phenylboronic acid containing hydrogels).