Glucose Monitoring In Diabetic Patients Research Articles

Individualized selection of recent glucose monitoring devices for self-management based on competitive features.

Goal of the study was to systematically review competitive advantages of medical devices for glucose monitoring in diabetic patients. The review is done systematically according to SALSA criteria and PRISMA guidelines. The search for eligible articles was held from February 16th 2023 to March 1st 2023 in Russian and English languages. The results were synthesized narratively, tabularly, and visually. The search was conducted in the following databases of scientific literature: PubMed, IEEE Xplore, Google Scholar, CyberLeninka, and eLibrary. Twenty-two out of fifty-two manuscripts met the inclusion criteria. The most promising and advantageous characteristics of the evaluated devices, as identified by researchers, include the following: the capability for noninvasive examination; features that facilitate use by patients with fine motor, hearing, and visual impairments; add-ons and software designed to improve patient compliance, including in pediatric populations; and device attributes that enhance the speed and accuracy of analysis while being free of iatrogenic effects. With increasing prevalence of diabetes, glycemic control is crucial for preventing complications. The market offers numerous glucose monitoring devices (GMDs) with varying features, making selection challenging. Our study systematically categorized the strengths of each GMD model for diabetic patients, aiding informed device selection.

Optical blood glucose non-invasive detection and its research progress.

Blood glucose concentration is an important index for the diagnosis of diabetes, its self-monitoring technology is the method for scientific diabetes management. Currently, the typical household blood glucose meters have achieved great success in diabetes management, but they are discrete detection methods, and involve invasive blood sampling procedures. Optical detection technologies, which use the physical properties of light to detect the glucose concentration in body fluids non-invasively, have shown great potential in non-invasive blood glucose detection. This article summarized and analyzed the basic principles, research status, existing problems, and application prospects of different optical glucose detection technologies. In addition, this article also discusses the problems of optical detection technology in wearable sensors and perspectives on the future of non-invasive blood glucose detection technology to improve blood glucose monitoring in diabetic patients.

Smartphone‐Based Noninvasive Glucose Monitoring in Diabetic Patients Utilizing Enhanced Chemiluminescence Imaging Technique

The current study aims for a simple, rapid, and smartphone‐based enhanced chemiluminescence (eCL) technique for sensitively detecting glucose in human urine. Herein, 1,3‐propanedithiol cross‐linked gold nanoparticles (GNPs‐PDT) via a simple reduction method is synthesized. Further, it is characterized by UV–vis spectroscopy and transmission electron microscopy. The synthesized GNPs‐PDT is found to possess oxidase mimetic activity and generate superoxide radicals from dissolved oxygen, which causes the oxidation of luminol to give a strong and stable CL signal. On the introduction of glucose into the reaction system, a CL quenching phenomenon is observed owing to the tendency of superoxide radicals to oxidize glucose into gluconic acid. Employing the quenching effect of glucose on the eCL signals, a sensor is designed for glucose detection in human urine samples. Under optimized conditions, the proposed method works in a dynamic range from 0.25 to 2 mM (R 2 = 0.98) with a detection limit of 0.36 mM. In addition, a simple and portable smartphone‐based imaging technique analyzed by Image J software for eCL‐based glucose sensing is proposed. The developed proof of concept provides good correlations of glucose detection in diabetic patients.

Role of continuous glucose monitoring in diabetic patients at high cardiovascular risk: an expert-based multidisciplinary Delphi consensus

BackgroundContinuous glucose monitoring (CGM) shows in more detail the glycaemic pattern of diabetic subjects and provides several new parameters (“glucometrics”) to assess patients’ glycaemia and consensually guide treatment. A better control of glucose levels might result in improvement of clinical outcome and reduce disease complications. This study aimed to gather an expert consensus on the clinical and prognostic use of CGM in diabetic patients at high cardiovascular risk or with heart disease.MethodsA list of 22 statements concerning type of patients who can benefit from CGM, prognostic impact of CGM in diabetic patients with heart disease, CGM use during acute cardiovascular events and educational issues of CGM were developed. Using a two-round Delphi methodology, the survey was distributed online to 42 Italian experts (21 diabetologists and 21 cardiologists) who rated their level of agreement with each statement on a 5-point Likert scale. Consensus was predefined as more than 66% of the panel agreeing/disagreeing with any given statement.ResultsForty experts (95%) answered the survey. Every statement achieved a positive consensus. In particular, the panel expressed the feeling that CGM can be prognostically relevant for every diabetic patient (70%) and that is clinically useful also in the management of those with type 2 diabetes not treated with insulin (87.5%). The assessment of time in range (TIR), glycaemic variability (GV) and hypoglycaemic/hyperglycaemic episodes were considered relevant in the management of diabetic patients with heart disease (92.5% for TIR, 95% for GV, 97.5% for time spent in hypoglycaemia) and can improve the prognosis of those with ischaemic heart disease (100% for hypoglycaemia, 90% for hyperglycaemia) or with heart failure (87.5% for hypoglycaemia, 85% for TIR, 87.5% for GV). The experts retained that CGM can be used and can impact the short- and long-term prognosis during an acute cardiovascular event. Lastly, CGM has a recognized educational role for diabetic subjects.ConclusionsAccording to this Delphi consensus, the clinical and prognostic use of CGM in diabetic patients at high cardiovascular risk is promising and deserves dedicated studies to confirm the experts’ feelings.

Sensitive Oxidation of Sorbitol-Mediated Fe2+ by H2O2: A Reliable TD-NMR Method for Clinical Blood Glucose Detection

The clinical challenge of high-accuracy blood glucose detection schemes is to overcome the detection error caused by the background interferences in different individuals. H2O2 as the specific product of glucose oxidation can be involved in the Fe2+/Fe3+ conversion and detected by the time-domain nuclear magnetic resonance (TD-NMR) method sensitively. But, in clinical applications, the oxidation of Fe2+ is susceptible to the complex sample substrates. In this work, we sorted out two kinds of possible interference mechanisms of Fe2+ oxidation in the NMR blood glucose detection method and proposed a feasible scheme that uses sorbitol to weaken the adverse effects of interference. We found that sorbitol-mediated Fe2+ can greatly enhance the sensitivity of the T2 value to H2O2. The chain reaction caused by sorbitol can significantly amplify the efficiency of Fe2+ oxidation at the same concentration of H2O2. Thereby, we can achieve the higher dilution multiple of serum samples to reduce the amount of interfering substances involved in the Fe2+/Fe3+ conversion. We justified the accuracy and availability of our method by successfully detecting and confirming the correlation between the T2 decrease and glucose concentration of the serum samples collected from 16 subjects. The sorbitol-Fe2+ glucose detection method with high sensitivity can be further combined with miniature NMR analyzers to satisfy the calibration requirements of glucose monitoring in diabetic patients instead of frequent medical visits.

Enhancing the Long-Term Stability of a Polymer Dot Glucose Transducer by Using an Enzymatic Cascade Reaction System.

Impaired glucose metabolism in diabetes causes severe acute and long-term complications, making real-time detection of blood glucose indispensable for diabetic patients. Existing continuous glucose monitoring systems are unsuitable for long-term clinical glycemic management due to poor long-term stability. Polymer dot (Pdot) glucose transducers are implantable optical nanosensors that exhibit excellent brightness, sensitivity, selectivity, and biocompatibility. Here, it is shown that hydrogen peroxide-a product of glucose oxidation in Pdot glucose sensors-degrades sensor performance via photobleaching, reduces glucose oxidase activity, and generates cytotoxicity. By adding catalase to a glucose oxidase-based Pdot sensor to create an enzymatic cascade, the hydrogen peroxide product of glucose oxidation is rapidly decomposed by catalase, preventing its accumulation and improving the sensor's photostability, enzymatic activity, and biocompatibility. Thus, a next-generation Pdot glucose transducer with a multienzyme reaction system (Pdot-GOx/CAT) that provides excellent sensing characteristics as well as greater detection system stability is presented. Pdot glucose transducers that incorporate this enzymatic cascade to eliminate hydrogen peroxide will possess greater long-term stability for improved continuous glucose monitoring in diabetic patients.

Surface Enhanced Raman Spectroscopy Based Biosensor with a Microneedle Array for Minimally Invasive In Vivo Glucose Measurements.

To monitor blood glucose levels reliably, diabetic patients usually have to undergo frequent fingerstick tests to draw out fresh blood, which is painful and inconvenient with the potential risk of cross contamination especially when the lancet is reused or not properly sterilized. This work reports a novel surface-enhanced Raman spectroscopy (SERS) sensor for the in situ intradermal detection of glucose based on a low-cost poly(methyl methacrylate) microneedle (PMMA MN) array. After incorporating 1-decanethiol (1-DT) onto the silver-coated array surface, the sensor was calibrated in the range of 0-20 mM in skin phantoms then tested for the in vivo quantification of glucose in a mouse model of streptozocin (STZ)-induced type I diabetes. The results showed that the functional poly(methyl methacrylate) microneedle (F-PMMA MN) array was able to directly measure glucose in the interstitial fluid (ISF) in a few minutes and retain its structural integrity without swelling. The Clarke error grid analysis of measured data indicated that 93% of the data points lie in zones A and B. Moreover, the MN array exhibited minimal invasiveness to the skin as the skin recovered well without any noticeable adverse reaction in 10 min after measurements. With further improvement and proper validation, this polymeric MN array-based SERS biosensor has the potential to be used in painless glucose monitoring of diabetic patients in the future.

Data Analysis and Accuracy Evaluation of a Continuous Glucose-Monitoring Device

This study was aimed at analyzing data and evaluating the accuracy of a new subcutaneous continuous glucose-monitoring device by referring to finger-pricking measurement. The data were obtained from 7 diabetic patients. An improved implanted flex sensor was used to measure the interstitial glucose concentration every 3 min within 6 days, and five finger-pricking samples were collected every day for comparison. A periodic glucose change happened every day. 2.45% of CGM values were in the hypoglycemic range (<70 mg/dl), 55.4% were in the normal range (70-180 mg/dl), and 42.15% were in the hyperglycemic range (>180 mg/dl). The interstitial glucose concentrations (n=204) were well linearly correlated with the capillary glucose concentrations (r=0.94, P<0.01), but a delay occurred between 10 and 40 minutes within two measurements (CGM later), and the individual average delay times were relatively close to 24.6 minutes. Clarke’s error grid analysis showed that 86.7% of the points fell in zone A, 12.7% fell in zone B, and only 0.6% fell in zone D. An overall MARD was 10.22%. This study demonstrated that the CGM was accurate and highly reliable; thus, it constituted a new device for continuous glucose monitoring in diabetic patients.

Hyaluronate-Gold Nanoparticle/Glucose Oxidase Complex for Highly Sensitive Wireless Noninvasive Glucose Sensors.

Noninvasive real-time biosensors to measure glucose levels in the body fluids have been widely investigated for continuous glucose monitoring of diabetic patients. However, they suffered from low sensitivity and reproducibility due to the instability of nanomaterials used for glucose biosensors. Here, we developed a hyaluronate-gold nanoparticle/glucose oxidase (HA-AuNP/GOx) complex and an ultralow-power application-specific integrated circuit chip for noninvasive and robust wireless patch-type glucose sensors. The HA-AuNP/GOx complex was prepared by the facile conjugation of thiolated HA to AuNPs and the following physical binding of GOx. The wireless glucose sensor exhibited slow water evaporation (0.11 μL/min), fast response (5 s), high sensitivity (12.37 μA·dL/mg·cm2) and selectivity, a low detection limit (0.5 mg/dL), and highly stable enzymatic activity (∼14 days). We successfully demonstrated the strong correlation between glucose concentrations measured by a commercially available blood glucometer and the wireless patch-type glucose sensor. Taken together, we could confirm the feasibility of the wireless patch-type robust glucose sensor for noninvasive and continuous diabetic diagnosis.

Development of a Glucose Sensor Using Palladium Electrode

An amperometric glucose sensor was introduced where glucose oxidase was immobilized on palladium electrode. This sensor based on the glucose oxidase catalyzed oxidation of glucose and electrochemical oxidation of hydrogen peroxide which was produced by enzyme reaction. Basic concept of the glucose sensor is composed of inner and outer membrane systems, immobilized glucose oxidase layer, and palladium electrode. Inner membrane prevents the access of electrochemical interfering substrates. Outer membrane works as a diffusion barrier of glucose. The glucose sensor can achieve a wide dynamic range with this outer membrane. In this research, to verify this concept especially the role of outer membrane, the glucose sensor which was made with palladium electrode, glucose oxidase layer, and outer membrane was tested on different glucose concentrations. The sensor showed a good correlation between sensor responses and glucose concentrations. In addition, the dynamic range of this sensor was enough for glucose monitoring of diabetic patients. This sensor also demonstrated stable sensor responses during several days. These results show that this sensor has a strong potential for application to continuous glucose monitoring, or CGM. Disclosure T. Han: Employee; Self; Panasonic Healthcare Co., Ltd. S. Noda: Employee; Self; Panasonic Healthcare Co., Ltd. K. Haneda: Employee; Self; Panasonic Healthcare Co., Ltd. N. Shigetou: Employee; Self; Panasonic Healthcare Co., Ltd.

Compliance Patterns and Utilization of e-Health for Glucose Monitoring: Standalone Internet Gateway and Tablet Device.

Knowledge regarding compliance patterns and service utilization in e-health is important for the development of effective services. To develop proper e-health, the characteristics of compliance patterns and utilization of e-health should be studied. We studied these for glucose monitoring of diabetic patients from primary clinics. Data were collected from 160 outpatients who participated in e-health for glucose monitoring funded by the Korean government. Specifically, this study focused on two device types: a standalone Internet gateway and a tablet device. The SPSS 18.0 software was used for statistical analyses of demographic characteristics, survival data, and Cox proportional hazards regression model. Standalone Internet gateway users demonstrated a more stable compliance pattern than did tablet device users. The compliance rate differed according to the device type. Typically, compliance decreases considerably around 8 months. In these results, standalone Internet gateway users utilized the service for longer periods than tablet device users. Gateway type and location also influenced utilization (p < 0.05). The service should be designed according to the device type to develop appropriate service models. Thus, service designers should understand the different characteristics of service devices. This study provides insight into compliance patterns and utilization to develop appropriate service models and service interventions depending on the device.

Brief communication (Original). Correlation of glycated albumin with self blood glucose monitoring in diabetic patients on hemodialysis taking erythropoietin

Abstract Background: Serum glycated albumin (GA) is a marker of glycemic control in diabetic renal patients, but studies were limited by the use of few random glucose values to define glycemic control. Objectives: To determine whether GA correlated with self blood glucose monitoring is better than HbA1c in hemodialyzed diabetic patients taking erythropoietin. Methods: This was a cross-sectional study of diabetic patients on hemodialysis with and without erythropoietin. GA was measured by ELISA and HbA1c by ion-exchange HPLC. GA was reported as the GA/albumin ratio where albumin was measured using bromocresol green. The average capillary blood glucose level over the preceding three months (CBG) was calculated from self-reported daily prebreakfast, prelunch, and prebed glucose meter readings. Results: Thirty-four patients were recruited; 18 were taking erythropoietin (6000 units per week) and 16 had never received erythropoietin. HbA1c correlated poorly with CBG in patients taking erythropoietin (r = -0.014, P = 0.96) compared with patients without erythropoietin (r = 0.579, P = 0.02). The correlation of GA/albumin ratio with CBG in the erythropoietin group (r = 0.612, P = 0.007) was similar to the nonerythropoietin group (r = 0.854, P &lt; 0.001). The slope for HbA1c versus CBG was 2.8-fold greater in patients without erythropoietin compared with those taking erythropoietin. There was no significant difference in the slopes for GA/albumin ratio versus CBG between the two patient groups (P &gt; 0.05). Conclusion: In diabetic patients on hemodialysis and taking low doses of erythropoietin, GA/albumin is a better marker of glycemic control than HbA1c.

W1419 Delayed Postprandial Hyperglycemia Assessed With Continuous Glucose Monitoring in Diabetic Patients Suggests Gastroparesis.

W1419 Delayed Postprandial Hyperglycemia Assessed With Continuous Glucose Monitoring in Diabetic Patients Suggests Gastroparesis.

Continuous Glucose Profiles in Healthy Subjects under Everyday Life Conditions and after Different Meals

This study investigated continuous glucose profiles in nondiabetic subjects. Continuous interstitial glucose measurement was performed under everyday life conditions (2 days) and after ingestion of four meals with standardized carbohydrate content (50 grams), but with different types of carbohydrates and variable protein and fat content. Twenty-four healthy volunteers (12 female, 12 male, age 27.1 +/- 3.6 years) participated in the study. Each subject wore two microdialysis devices (SCGM1, Roche Diagnostics) simultaneously. The mean 24-hour interstitial glucose concentration under everyday life conditions was 89.3 +/- 6.2 mg/dl (mean +/- SD, n = 21), and mean interstitial glucose concentrations at daytime and during the night were 93.0 +/- 7.0 and 81.8 +/- 6.3 mg/dl, respectively. The highest postprandial glucose concentrations were observed after breakfast: 132.3 +/- 16.7 mg/dl (range 101-168 mg/dl); peak concentrations after lunch and dinner were 118.2 +/- 13.4 and 123.0 +/- 16.9 mg/dl, respectively. Mean time to peak glucose concentration was between 46 and 50 minutes. After ingestion of standardized meals with fast absorption characteristics, peak interstitial glucose concentrations were 133.2 +/- 14.4 and 137.2 +/- 21.1 mg/dl, respectively. Meals with a higher fiber, protein, and fat content induced a smaller increase and a slower decrease of postprandial glucose concentrations with peak values of 99.2 +/- 10.5 and 122.1 +/- 20.4 mg/dl, respectively. This study provided continuous glucose profiles in nondiabetic subjects and demonstrated that differences in meal composition are reflected in postprandial interstitial glucose concentrations. Regarding the increasing application of continuous glucose monitoring in diabetic patients, these data suggest that detailed information about the ingested meals is important for adequate interpretation of postprandial glucose profiles.

Toward continuous glucose monitoring with planar modified biosensors and microdialysis: Study of temperature, oxygen dependence and in vivo experiment

Glucose biosensors based on the use of planar screen-printed electrodes modified with an electrochemical mediator and with glucose oxidase have been optimised for their application in the continuous glucose monitoring in diabetic patients. A full study of their operative stability and temperature dependence has been accomplished, thus giving useful information for in vivo applications. The effect of dissolved oxygen concentration in the working solution was also studied in order to evaluate its effect on the linearity of the sensors. Glucose monitoring performed with serum samples was performed to evaluate the effect of matrix components on operative stability and demonstrated an efficient behaviour for 72 h of continuous monitoring. Finally, these studies led to a sensor capable of detecting glucose at concentrations as low as 0.04 mM and with a good linearity up to 2.0 mM (at 37 °C) with an operative stability of ca. 72 h, thus demonstrating the possible application of these sensors for continuous glucose monitoring in conjunction with a microdialysis probe. Moreover, preliminary in vivo experiments for ca. 20 h have demonstrated the feasibility of this system.

Hyperglycemia, Nutrition Support, and Acute Illness

The impact of short-term hyperglycemia on morbidity and mortality of hospitalized patients has gained significant attention from clinicians since the landmark prospective, randomized clinical trial by van den Berghe et al, which demonstrated dramatic improvements in morbidity and mortality in critically ill surgical patients with improved glycemic control (80–110 mg/dL) compared to historically accepted glucose targets (180–200 mg/dL). Stress-induced hyperglycemia is a common phenomenon often observed in acutely ill patient populations due to impairments in insulin-mediated glucose uptake in the skeletal muscle, and failure of insulin to suppress hepatic gluconeogenesis. Parenteral nutrition (PN) is frequently a component of care for these patients and, because of its appreciable dextrose load, may further promote elevations in blood glucose. Clinicians responsible for PN administration face daily decisions over how to optimally manage their patients’ glycemic control. Although the overall impact of tight management has been demonstrated in surgical intensive care unit (ICU) patients, the potentially adverse contributions of PN have not been characterized in the setting of appropriate glycemic control and methods for optimal management have yet to be discerned. The purpose of the American Society of Parenteral and Enteral Nutrition 2005 research workshop sponsored by NIDDK (DK06190-04) on Hyperglycemia, Nutrition Support and Acute Illness was to summarize the research that had been conducted on glucose management in hospitalized patients, to describe the pathophysiology that induces the stress-induced hyperglycemia with a focus on the role of the inflammation and the immune system, and to describe protocols that have been endorsed by the American Diabetes Association for glucose monitoring in diabetic patients as well as others that have been utilized by clinicians and researchers providing nutrition support to the critically ill. The ultimate objective of the program was to provide clinical guidelines for optimal glycemic management based upon the current scientific knowledge. The next several issues of JPEN will include papers that were presented at this workshop. In this issue, Dr Jeffrey Mechanick presents the mechanisms of hyperglycemia in acutely ill patients. A comprehensive model of glucose allostasis, immunoneuroendocrine axis activation, and insulin receptor signal transduction is described. The “healthy chaos” that underlies the complex, interactive stress response is introduced, with the caveat that failure to recognize its importance can inject unintentional harm. This article is followed by Dr Anastassios Pittas’ meta-analysis of randomized controlled trials that investigated the impact of insulin therapy on mortality in critically ill patients. Included are trials conducted in cardiac ICU patients that received glucose-insulin and potassium replacement therapies. Also presented are randomized trials in critically ill patients which utilized more aggressive insulin management to achieve improved glycemic control vs those which utilized conventional insulin management and secured less rigid glucose control. The potential benefits of insulin therapy compared to euglycemia were also explored in discussing these trials. It is hoped that readers will find the summaries from the research workshop that are included in the next several JPEN issues useful in highlighting the high priority for improved glycemic control in critically ill patients. We further anticipate that these papers will serve to emphasize the many important research questions that remain, and will help to foster development of a future research agenda. While PN has proven to be life-saving in humans with permanent gastrointestinal failure, it also has well-recognized inherent risks. It is possible that many of the perceived risks of PN will be largely alleviated with more stringent attention to glycemic control.

Making glucose oxidase fit for biofuel cell applications by directed protein evolution

Progress in miniature chip-design raises demands for implantable power sources in health care applications such as continuous glucose monitoring of diabetic patients. Pioneered by Adam Heller, miniaturized enzymatic biofuel cells (mBCs) convert blood sugars into electrical energy by employing for example glucose oxidase (GOx) on the anode and bilirubin oxidase on the cathode. To match application demands it is crucial to increase lifetime and power output of mBCs. The power output has been limited by the performance of GOx on the anode. We developed a glucose oxidase detection assay (GODA) as medium-throughput screening system for improving GOx properties by directed protein evolution. GODA is a reaction product detection assay based on coupled enzymatic reactions leading to NADPH formation which is recorded at 340 nm. The main advantage of the assay is that it detects the production of d-gluconolactone instead of the side-product hydrogen peroxide and enables to improve bioelectrochemical properties of GOx. For validating the screening system, a mutagenic library of GOx from Aspergillus niger (EC 1.1.3.4) was generated and screened for improved activity using Saccharomyces cerevisiae as host. Directed evolution resulted in a GOx mutant I115V with 1.4-1.5-fold improved activity for beta-d-glucose (Vmax from 7.94 to 10.81 micromol min(-1) mg(-1); Km approximately 19-21 mM) and oxygen consumption kinetics correlate well [Vmax (O2) from 5.94 to 8.34 micromol min(-1) mg(-1); Km (O2) from 700 to 474 microM]. The developed mutagenic protocol and GODA represent a proof-of-principle that GOx can be evolved by directed evolution in S. cerevisiae for putative use in biofuel cells.

光音響法によるグルコースモニタリング

Photoacoustic spectroscopy is an alternative technique for noninvasive glucose monitoring of diabetic patients. The incident near-infrared light penetrates a few millimeters into human tissue and generates an acoustic wave that is derived from the optical absorption. The photoacoustic signal is detected by a piezoelectric transducer, and the glucose concentration in human tissue is estimated from the magnitude of the signal. Several studies have been carried out to eliminate the numerous optically interfering components in human blood and tissue. In this paper, in vivo and in vitro photoacoustic measurements of glucose are reviewed and a highly sensitive photoacoustic sensor that uses a Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZNT91/9) single crystal with an extremely large piezoelectric constant g33 is described.

A microdialysis technique for continuous subcutaneous glucose monitoring in diabetic patients (part 2)

The aim of this study was to evaluate the reproducibility, the accuracy and the reliability of a continuous subcutaneous glucose measuring system. The GlucoDay® system (A. Menarini I.F.R. S.r.l.—Florence, Italy) is a portable instrument provided with a micro-pump and a biosensor, coupled to a microdialysis system (see part 1). This instrument has demonstrated high reliability coupled with a low degree of invasivity. The profiles of glucose monitoring allow to achieve an excellent knowledge of the real variation of glucose in diabetic patients. The reproducibility study showed a bias lower than 10% between instruments. The accuracy study showed a difference from the reference method lower than 15%.

A microdialysis technique for continuous subcutaneous glucose monitoring in diabetic patients (part 1)

The performances and the stability of a novel subcutaneous glucose monitoring system have been evaluated. GlucoDay® (A. Menarini I.F.R. S.r.l, Florence Italy) is a portable instrument provided with a micro-pump and a biosensor coupled to a microdialysis system capable of recording the subcutaneous glucose level every 3 min. Long and short term stability of the biosensor are discussed and the results of some critical in vitro and in vivo (on rabbits) experiments are reported. A linear response up to 30 mM has been found for in vivo glucose concentration. The sensitivity referred to blood glucose is better than 0.1 mM and the zero current is typically below the equivalent of 0.1 mM. In the accuracy study a mean bias of 2.7 mg/dl and a correlation coefficient equal to 0.9697 have been found. At room temperature, an excellent membrane stability assures good performances up to 6 months from the first use.