Guido Freckmann - Academia.edu (original) (raw)

Papers by Guido Freckmann

Research paper thumbnail of Untersuchung der Messgenauigkeit 12 verschiedener Systeme zur Blutglukose-Selbstmessung nach ISO 15197

Diabetologie und Stoffwechsel, 2010

Research paper thumbnail of Kontinuierliche subkutane Glukosemessung bei gesunden Probanden nach standardisierten Mahlzeiten und unter Alltagsbedingungen

Diabetologie und Stoffwechsel, 2007

Research paper thumbnail of Influence of partial pressure of oxygen in blood samples on measurement performance in glucose-oxidase-based systems for self-monitoring of blood glucose

Journal of diabetes science and technology, 2013

Partial pressure of oxygen (pO2) in blood samples can affect blood glucose (BG) measurements, par... more Partial pressure of oxygen (pO2) in blood samples can affect blood glucose (BG) measurements, particularly in systems that employ the glucose oxidase (GOx) enzyme reaction on test strips. In this study, we assessed the impact of different pO2 values on the performance of five GOx systems and one glucose dehydrogenase (GDH) system. Two of the GOx systems are labeled by the manufacturers to be sensitive to increased blood oxygen content, while the other three GOx systems are not. Aliquots of 20 venous samples were adjusted to the following pO2 values: <45, ~70, and ≥150 mmHg. For each system, five consecutive measurements on each sample aliquot were performed using the same test strip lot. Relative differences between the mean BG results at pO2 ~70 mmHg, which is considered to be similar to pO2 in capillary blood samples, and the mean BG result at pO2 <45 and ≥150 mmHg were calculated. For all tested GOx systems, mean relative differences in the BG measurement results were betwe...

Research paper thumbnail of Self-monitoring of blood glucose: impact of a time delay between capillary blood sampling and glucose measurement

Journal of diabetes science and technology, 2014

Research paper thumbnail of System accuracy evaluation of systems for point-of-care testing of blood glucose: a comparison of a patient-use system with six professional-use systems

Clinical Chemistry and Laboratory Medicine, 2000

Background: Point-of-care testing (POCT) of blood glucose (BG) is performed by medical personnel ... more Background: Point-of-care testing (POCT) of blood glucose (BG) is performed by medical personnel in clinical settings as well as by patients themselves for self-monitoring of blood glucose (SMBG) at home. We investigated if a system mainly intended for SMBG by people with diabetes, but also suitable for BG measurements by medical personnel, can achieve measurement accuracy on capillary blood samples comparable with professional-use POCT systems. Methods: System accuracy was evaluated under standardised conditions, following the ISO standard 15197:2003.

Research paper thumbnail of Impact of partial pressure of oxygen in blood samples on the performance of systems for self-monitoring of blood glucose

Diabetes technology & therapeutics, 2014

The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen... more The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample. Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ≤45 mm Hg, approximately 70 mm Hg, and ≥150 mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70 mm Hg, which was considered to be similar to pO2 values in capillary blood samples,...

Research paper thumbnail of Accuracy Evaluation of Four Blood Glucose Monitoring Systems in Unaltered Blood Samples in the Low Glycemic Range and Blood Samples in the Concentration Range Defined by ISO 15197

Diabetes Technology & Therapeutics, 2015

Systems for self-monitoring of blood glucose (SMBG) are expected to be accurate enough to provide... more Systems for self-monitoring of blood glucose (SMBG) are expected to be accurate enough to provide reliable measurement results. Especially in the low glycemic range, adequate therapeutic decisions based on reliable results can alleviate complications associated with hypoglycemia. The accuracy of four SMBG systems (system 1 was the ACCU-CHEK(®) Aviva [Roche Diagnostics GmbH, Mannheim, Germany], system 2 was the Contour(®) XT [Bayer Consumer Care AG, Basel, Switzerland], system 3 was the GlucoCheck XL [aktivmed GmbH, Augsberg, Germany], and system 4 was the GlucoMen(®) LX PLUS [A. Menarini Diagnostics S.r.l., Florence, Italy]) with three test-strip lots each was evaluated by calculating mean absolute relative differences (MARDs). Two datasets were evaluated: (1) 100 samples with blood glucose concentrations &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;70 mg/dL and (2) 100 samples distributed following International Organization for Standardization (ISO) standard 15197. Each sample was measured twice with each test-strip lot of each SMBG system. Comparison measurement results were obtained with a glucose oxidase method and a hexokinase method, both traceable according to ISO 17511. Analysis of variance of the MARD between the SMBG system and the comparison method was performed. MARD values ranged from 4.4% to 13.4% (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;70 mg/dL) and 4.8% to 8.9% (ISO 15197-distributed) and differed significantly, with systems 1 and 2 showing lower MARDs than systems 3 and 4. MARD values deviated by up to 2.5% (corresponding to a relative deviation of approximately 40%) between the two comparison methods. The investigated SMBG systems showed a significant variation of accuracy (measured by MARD), especially with higher MARD values in the low glycemic range. The selected comparison method had an impact on the MARD and therefore on the apparent accuracy of the SMBG systems. Sufficient measurement accuracy in the low glycemic range is required to enable users to react adequately to hypoglycemia.

Research paper thumbnail of System Accuracy Evaluation of Different Blood Glucose Monitoring Systems Following ISO 15197:2013 by Using Two Different Comparison Methods

Diabetes technology & therapeutics, Jan 25, 2015

Adherence to established standards (e.g., International Organization for Standardization [ISO] 15... more Adherence to established standards (e.g., International Organization for Standardization [ISO] 15197) is important to ensure comparable and sufficient accuracy of systems for self-monitoring of blood glucose (SMBG). Accuracy evaluation was performed for different SMBG systems available in Europe with three reagent lots each. Test procedures followed the recently published revision ISO 15197:2013. Comparison measurements were performed with a glucose oxidase (YSI 2300 STAT Plus™ glucose analyzer; YSI Inc., Yellow Springs, OH) and a hexokinase (cobas Integra(®) 400 Plus analyzer; Roche Instrument Center, Rotkreuz, Switzerland) method. Compliance with ISO 15197:2013 accuracy criteria was determined by calculating the percentage of results within ±15% or within ±0.83 mmol/L of the comparison measurement results for glucose concentrations at and above or below 5.55 mmol/L, respectively, and by calculating the percentage of results within consensus error grid Zones A and B. Seven systems ...

Research paper thumbnail of Performance of Blood Glucose Meters in the Low-Glucose Range: Current Evaluations Indicate That It Is Not Sufficient From a Clinical Point of View

Diabetes care, Jan 15, 2015

Research paper thumbnail of ISO 15197:2013 Accuracy Evaluation of Two CE-Marked Systems for Self-Monitoring of Blood Glucose

Journal of diabetes science and technology, Jan 21, 2015

Research paper thumbnail of System Accuracy Evaluation of Four Systems for Self-Monitoring of Blood Glucose Following ISO 15197 Using a Glucose Oxidase and a Hexokinase-Based Comparison Method

Journal of diabetes science and technology, Jan 14, 2015

The standard ISO (International Organization for Standardization) 15197 is widely accepted for th... more The standard ISO (International Organization for Standardization) 15197 is widely accepted for the accuracy evaluation of systems for self-monitoring of blood glucose (SMBG). Accuracy evaluation was performed for 4 SMBG systems (Accu-Chek® Aviva, Contour®XT, GlucoCheck XL, GlucoMen® LX PLUS) with 3 test strip lots each. To investigate a possible impact of the comparison method on system accuracy data, 2 different established methods were used. The evaluation was performed in a standardized manner following test procedures described in ISO 15197:2003 (section 7.3). System accuracy was assessed by applying ISO 15197:2003 and in addition ISO 15197:2013 criteria (section 6.3.3). For each system, comparison measurements were performed with a glucose oxidase (YSI 2300 STAT Plus™ glucose analyzer) and a hexokinase (cobas® c111) method. All 4 systems fulfilled the accuracy requirements of ISO 15197:2003 with the tested lots. More stringent accuracy criteria of ISO 15197:2013 were fulfilled ...

Research paper thumbnail of Rate-of-Change Dependence of the Performance of Two CGM Systems During Induced Glucose Swings

Journal of diabetes science and technology, Jan 7, 2015

The accuracy of continuous glucose monitoring (CGM) systems is often assessed with respect to blo... more The accuracy of continuous glucose monitoring (CGM) systems is often assessed with respect to blood glucose (BG) readings. CGM readings are affected by a physiological and a technical time delay when compared to BG readings. In this analysis, the dependence of CGM performance parameters on the BG rate of change was investigated for 2 CGM systems. Data from a previously published study were retrospectively analyzed. An established CGM system (Dexcom G4, Dexcom, San Diego, CA; system A) and a prototype system (Roche Diagnostics GmbH, Mannheim, Germany; system B) with 2 sensors each were worn by 10 subjects in parallel. Glucose swings were induced to achieve rapidly changing BG concentrations. Mean absolute relative differences (MARD) were calculated in different BG rate-of-change categories. In addition, sensor-to-sensor precision was assessed. At BG rates of change of -1 mg/dl/min to 0 mg/dl/min and 0 mg/dl/min to +1 mg/dl/min, MARD results were 12.6% and 11.3% for system A and 8.2% ...

Research paper thumbnail of Quality of HbA1c Measurement in the Practice: The German Perspective

Journal of diabetes science and technology, Jan 17, 2015

Hemoglobin A1c (HbA1c) measurement has come to be a cornerstone in modern diabetes therapy. Howev... more Hemoglobin A1c (HbA1c) measurement has come to be a cornerstone in modern diabetes therapy. However, the methodological aspects of this type of measurement have been given little attention lately due to its position as an established method of choice. Nevertheless, quite a number of issues face practical application, such as clinically relevant differences between different measurement methods-both lab-based and point-of-care (POCT) systems will show better or worse diabetes management results after switching methods; and there are a number of possible reasons that need to be known and observed in practice. The aim of this review is to draw attention to these problems from a German point of view and provide suggestions for appropriate measures to improve the situation.

Research paper thumbnail of Use of microdialysis-based continuous glucose monitoring to drive real-time semi-closed-loop insulin infusion

Journal of diabetes science and technology, 2014

Continuous glucose monitoring (CGM) and automated insulin delivery may make diabetes management s... more Continuous glucose monitoring (CGM) and automated insulin delivery may make diabetes management substantially easier, if the quality of the resulting therapy remains adequate. In this study, a semi-closed-loop control algorithm was used to drive insulin therapy and its quality was compared to that of subject-directed therapy. Twelve subjects stayed at the study site for approximately 70 hours and were provided with the investigational Automated Pancreas System Test Stand (APS-TS), which was used to calculate insulin dosage recommendations automatically. These recommendations were based on microdialysis CGM values and common diabetes therapy parameters. For the first half of their stay, the subjects directed their diabetes therapy themselves, whereas for the second half, the insulin recommendations were delivered by the APS-TS (so-called algorithm-driven therapy). During subject-directed therapy, the mean glucose was 114 mg/dl compared to 125 mg/dl during algorithm-driven therapy. Ti...

Research paper thumbnail of Accuracy assessment of an advanced blood glucose monitoring system for self-testing with three reagent system lots following ISO 15197:2013

Journal of diabetes science and technology, 2014

Research paper thumbnail of Accuracy assessment of two novel systems for self-monitoring of blood glucose following ISO 15197:2013

Journal of diabetes science and technology, 2014

Research paper thumbnail of Partial pressure of oxygen in capillary blood samples from the fingertip

Journal of diabetes science and technology, 2013

Research paper thumbnail of Evaluation of 12 blood glucose monitoring systems for self-testing: system accuracy and measurement reproducibility

Diabetes technology & therapeutics, 2014

Systems for self-monitoring of blood glucose (SMBG) have to provide accurate and reproducible blo... more Systems for self-monitoring of blood glucose (SMBG) have to provide accurate and reproducible blood glucose (BG) values in order to ensure adequate therapeutic decisions by people with diabetes. Twelve SMBG systems were compared in a standardized manner under controlled laboratory conditions: nine systems were available on the German market and were purchased from a local pharmacy, and three systems were obtained from the manufacturer (two systems were available on the U.S. market, and one system was not yet introduced to the German market). System accuracy was evaluated following DIN EN ISO (International Organization for Standardization) 15197:2003. In addition, measurement reproducibility was assessed following a modified TNO (Netherlands Organization for Applied Scientific Research) procedure. Comparison measurements were performed with either the glucose oxidase method (YSI 2300 STAT Plus™ glucose analyzer; YSI Life Sciences, Yellow Springs, OH) or the hexokinase method (cobas(...

Research paper thumbnail of Performance evaluation of three continuous glucose monitoring systems: comparison of six sensors per subject in parallel

Journal of diabetes science and technology, 2013

This study is aimed at comparing the performance of three continuous glucose monitoring (CGM) sys... more This study is aimed at comparing the performance of three continuous glucose monitoring (CGM) systems following the Clinical and Laboratory Standards Institute's POCT05-A guideline, which provides recommendations for performance evaluation of CGM systems. A total of 12 subjects with type 1 diabetes were enrolled in this study. Each subject wore six CGM systems in parallel, two sensors of each CGM system [FreeStyle Navigator™ (Navigator), MiniMed Guardian® REAL-Time with Enlite sensor (Guardian), DexCom™ Seven® Plus 3rd generation (Seven Plus)]. Each sensor was used for the lifetime specified by the manufacturer. To follow POCT05-A recommendations, glucose excursions were induced on two separate occasions, and venous and capillary blood glucose (BG) concentrations were obtained every 15 min for five consecutive hours. Capillary BG concentrations were measured at least once per hour during the day and once at night. Parameters investigated were CGM-to-BG differences [mean absolute...

Research paper thumbnail of Performance evaluation of a continuous glucose monitoring system under conditions similar to daily life

Journal of diabetes science and technology, 2013

This study aimed at evaluating and comparing the performance of a new generation of continuous gl... more This study aimed at evaluating and comparing the performance of a new generation of continuous glucose monitoring (CGM) system versus other CGM systems, under daily lifelike conditions. A total of 10 subjects (7 female) were enrolled in this study. Each subject wore two Dexcom G4™ CGM systems in parallel for the sensor lifetime specified by the manufacturer (7 days) to allow assessment of sensor-to-sensor precision. Capillary blood glucose (BG) measurements were performed at least once per hour during daytime and once at night. Glucose excursions were induced on two occasions. Performance was assessed by calculating the mean absolute relative difference (MARD) between CGM readings and paired capillary BG readings and precision absolute relative difference (PARD), i.e., differences between paired CGM readings. Overall aggregate MARD was 11.0% (n = 2392). Aggregate MARD for BG <70 mg/dl was 13.7%; for BG between 70 and 180 mg/dl, MARD was 11.4%; and for BG >180 mg/dl, MARD was 8...

Research paper thumbnail of Untersuchung der Messgenauigkeit 12 verschiedener Systeme zur Blutglukose-Selbstmessung nach ISO 15197

Diabetologie und Stoffwechsel, 2010

Research paper thumbnail of Kontinuierliche subkutane Glukosemessung bei gesunden Probanden nach standardisierten Mahlzeiten und unter Alltagsbedingungen

Diabetologie und Stoffwechsel, 2007

Research paper thumbnail of Influence of partial pressure of oxygen in blood samples on measurement performance in glucose-oxidase-based systems for self-monitoring of blood glucose

Journal of diabetes science and technology, 2013

Partial pressure of oxygen (pO2) in blood samples can affect blood glucose (BG) measurements, par... more Partial pressure of oxygen (pO2) in blood samples can affect blood glucose (BG) measurements, particularly in systems that employ the glucose oxidase (GOx) enzyme reaction on test strips. In this study, we assessed the impact of different pO2 values on the performance of five GOx systems and one glucose dehydrogenase (GDH) system. Two of the GOx systems are labeled by the manufacturers to be sensitive to increased blood oxygen content, while the other three GOx systems are not. Aliquots of 20 venous samples were adjusted to the following pO2 values: <45, ~70, and ≥150 mmHg. For each system, five consecutive measurements on each sample aliquot were performed using the same test strip lot. Relative differences between the mean BG results at pO2 ~70 mmHg, which is considered to be similar to pO2 in capillary blood samples, and the mean BG result at pO2 <45 and ≥150 mmHg were calculated. For all tested GOx systems, mean relative differences in the BG measurement results were betwe...

Research paper thumbnail of Self-monitoring of blood glucose: impact of a time delay between capillary blood sampling and glucose measurement

Journal of diabetes science and technology, 2014

Research paper thumbnail of System accuracy evaluation of systems for point-of-care testing of blood glucose: a comparison of a patient-use system with six professional-use systems

Clinical Chemistry and Laboratory Medicine, 2000

Background: Point-of-care testing (POCT) of blood glucose (BG) is performed by medical personnel ... more Background: Point-of-care testing (POCT) of blood glucose (BG) is performed by medical personnel in clinical settings as well as by patients themselves for self-monitoring of blood glucose (SMBG) at home. We investigated if a system mainly intended for SMBG by people with diabetes, but also suitable for BG measurements by medical personnel, can achieve measurement accuracy on capillary blood samples comparable with professional-use POCT systems. Methods: System accuracy was evaluated under standardised conditions, following the ISO standard 15197:2003.

Research paper thumbnail of Impact of partial pressure of oxygen in blood samples on the performance of systems for self-monitoring of blood glucose

Diabetes technology & therapeutics, 2014

The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen... more The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample. Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ≤45 mm Hg, approximately 70 mm Hg, and ≥150 mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70 mm Hg, which was considered to be similar to pO2 values in capillary blood samples,...

Research paper thumbnail of Accuracy Evaluation of Four Blood Glucose Monitoring Systems in Unaltered Blood Samples in the Low Glycemic Range and Blood Samples in the Concentration Range Defined by ISO 15197

Diabetes Technology & Therapeutics, 2015

Systems for self-monitoring of blood glucose (SMBG) are expected to be accurate enough to provide... more Systems for self-monitoring of blood glucose (SMBG) are expected to be accurate enough to provide reliable measurement results. Especially in the low glycemic range, adequate therapeutic decisions based on reliable results can alleviate complications associated with hypoglycemia. The accuracy of four SMBG systems (system 1 was the ACCU-CHEK(®) Aviva [Roche Diagnostics GmbH, Mannheim, Germany], system 2 was the Contour(®) XT [Bayer Consumer Care AG, Basel, Switzerland], system 3 was the GlucoCheck XL [aktivmed GmbH, Augsberg, Germany], and system 4 was the GlucoMen(®) LX PLUS [A. Menarini Diagnostics S.r.l., Florence, Italy]) with three test-strip lots each was evaluated by calculating mean absolute relative differences (MARDs). Two datasets were evaluated: (1) 100 samples with blood glucose concentrations &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;70 mg/dL and (2) 100 samples distributed following International Organization for Standardization (ISO) standard 15197. Each sample was measured twice with each test-strip lot of each SMBG system. Comparison measurement results were obtained with a glucose oxidase method and a hexokinase method, both traceable according to ISO 17511. Analysis of variance of the MARD between the SMBG system and the comparison method was performed. MARD values ranged from 4.4% to 13.4% (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;70 mg/dL) and 4.8% to 8.9% (ISO 15197-distributed) and differed significantly, with systems 1 and 2 showing lower MARDs than systems 3 and 4. MARD values deviated by up to 2.5% (corresponding to a relative deviation of approximately 40%) between the two comparison methods. The investigated SMBG systems showed a significant variation of accuracy (measured by MARD), especially with higher MARD values in the low glycemic range. The selected comparison method had an impact on the MARD and therefore on the apparent accuracy of the SMBG systems. Sufficient measurement accuracy in the low glycemic range is required to enable users to react adequately to hypoglycemia.

Research paper thumbnail of System Accuracy Evaluation of Different Blood Glucose Monitoring Systems Following ISO 15197:2013 by Using Two Different Comparison Methods

Diabetes technology & therapeutics, Jan 25, 2015

Adherence to established standards (e.g., International Organization for Standardization [ISO] 15... more Adherence to established standards (e.g., International Organization for Standardization [ISO] 15197) is important to ensure comparable and sufficient accuracy of systems for self-monitoring of blood glucose (SMBG). Accuracy evaluation was performed for different SMBG systems available in Europe with three reagent lots each. Test procedures followed the recently published revision ISO 15197:2013. Comparison measurements were performed with a glucose oxidase (YSI 2300 STAT Plus™ glucose analyzer; YSI Inc., Yellow Springs, OH) and a hexokinase (cobas Integra(®) 400 Plus analyzer; Roche Instrument Center, Rotkreuz, Switzerland) method. Compliance with ISO 15197:2013 accuracy criteria was determined by calculating the percentage of results within ±15% or within ±0.83 mmol/L of the comparison measurement results for glucose concentrations at and above or below 5.55 mmol/L, respectively, and by calculating the percentage of results within consensus error grid Zones A and B. Seven systems ...

Research paper thumbnail of Performance of Blood Glucose Meters in the Low-Glucose Range: Current Evaluations Indicate That It Is Not Sufficient From a Clinical Point of View

Diabetes care, Jan 15, 2015

Research paper thumbnail of ISO 15197:2013 Accuracy Evaluation of Two CE-Marked Systems for Self-Monitoring of Blood Glucose

Journal of diabetes science and technology, Jan 21, 2015

Research paper thumbnail of System Accuracy Evaluation of Four Systems for Self-Monitoring of Blood Glucose Following ISO 15197 Using a Glucose Oxidase and a Hexokinase-Based Comparison Method

Journal of diabetes science and technology, Jan 14, 2015

The standard ISO (International Organization for Standardization) 15197 is widely accepted for th... more The standard ISO (International Organization for Standardization) 15197 is widely accepted for the accuracy evaluation of systems for self-monitoring of blood glucose (SMBG). Accuracy evaluation was performed for 4 SMBG systems (Accu-Chek® Aviva, Contour®XT, GlucoCheck XL, GlucoMen® LX PLUS) with 3 test strip lots each. To investigate a possible impact of the comparison method on system accuracy data, 2 different established methods were used. The evaluation was performed in a standardized manner following test procedures described in ISO 15197:2003 (section 7.3). System accuracy was assessed by applying ISO 15197:2003 and in addition ISO 15197:2013 criteria (section 6.3.3). For each system, comparison measurements were performed with a glucose oxidase (YSI 2300 STAT Plus™ glucose analyzer) and a hexokinase (cobas® c111) method. All 4 systems fulfilled the accuracy requirements of ISO 15197:2003 with the tested lots. More stringent accuracy criteria of ISO 15197:2013 were fulfilled ...

Research paper thumbnail of Rate-of-Change Dependence of the Performance of Two CGM Systems During Induced Glucose Swings

Journal of diabetes science and technology, Jan 7, 2015

The accuracy of continuous glucose monitoring (CGM) systems is often assessed with respect to blo... more The accuracy of continuous glucose monitoring (CGM) systems is often assessed with respect to blood glucose (BG) readings. CGM readings are affected by a physiological and a technical time delay when compared to BG readings. In this analysis, the dependence of CGM performance parameters on the BG rate of change was investigated for 2 CGM systems. Data from a previously published study were retrospectively analyzed. An established CGM system (Dexcom G4, Dexcom, San Diego, CA; system A) and a prototype system (Roche Diagnostics GmbH, Mannheim, Germany; system B) with 2 sensors each were worn by 10 subjects in parallel. Glucose swings were induced to achieve rapidly changing BG concentrations. Mean absolute relative differences (MARD) were calculated in different BG rate-of-change categories. In addition, sensor-to-sensor precision was assessed. At BG rates of change of -1 mg/dl/min to 0 mg/dl/min and 0 mg/dl/min to +1 mg/dl/min, MARD results were 12.6% and 11.3% for system A and 8.2% ...

Research paper thumbnail of Quality of HbA1c Measurement in the Practice: The German Perspective

Journal of diabetes science and technology, Jan 17, 2015

Hemoglobin A1c (HbA1c) measurement has come to be a cornerstone in modern diabetes therapy. Howev... more Hemoglobin A1c (HbA1c) measurement has come to be a cornerstone in modern diabetes therapy. However, the methodological aspects of this type of measurement have been given little attention lately due to its position as an established method of choice. Nevertheless, quite a number of issues face practical application, such as clinically relevant differences between different measurement methods-both lab-based and point-of-care (POCT) systems will show better or worse diabetes management results after switching methods; and there are a number of possible reasons that need to be known and observed in practice. The aim of this review is to draw attention to these problems from a German point of view and provide suggestions for appropriate measures to improve the situation.

Research paper thumbnail of Use of microdialysis-based continuous glucose monitoring to drive real-time semi-closed-loop insulin infusion

Journal of diabetes science and technology, 2014

Continuous glucose monitoring (CGM) and automated insulin delivery may make diabetes management s... more Continuous glucose monitoring (CGM) and automated insulin delivery may make diabetes management substantially easier, if the quality of the resulting therapy remains adequate. In this study, a semi-closed-loop control algorithm was used to drive insulin therapy and its quality was compared to that of subject-directed therapy. Twelve subjects stayed at the study site for approximately 70 hours and were provided with the investigational Automated Pancreas System Test Stand (APS-TS), which was used to calculate insulin dosage recommendations automatically. These recommendations were based on microdialysis CGM values and common diabetes therapy parameters. For the first half of their stay, the subjects directed their diabetes therapy themselves, whereas for the second half, the insulin recommendations were delivered by the APS-TS (so-called algorithm-driven therapy). During subject-directed therapy, the mean glucose was 114 mg/dl compared to 125 mg/dl during algorithm-driven therapy. Ti...

Research paper thumbnail of Accuracy assessment of an advanced blood glucose monitoring system for self-testing with three reagent system lots following ISO 15197:2013

Journal of diabetes science and technology, 2014

Research paper thumbnail of Accuracy assessment of two novel systems for self-monitoring of blood glucose following ISO 15197:2013

Journal of diabetes science and technology, 2014

Research paper thumbnail of Partial pressure of oxygen in capillary blood samples from the fingertip

Journal of diabetes science and technology, 2013

Research paper thumbnail of Evaluation of 12 blood glucose monitoring systems for self-testing: system accuracy and measurement reproducibility

Diabetes technology & therapeutics, 2014

Systems for self-monitoring of blood glucose (SMBG) have to provide accurate and reproducible blo... more Systems for self-monitoring of blood glucose (SMBG) have to provide accurate and reproducible blood glucose (BG) values in order to ensure adequate therapeutic decisions by people with diabetes. Twelve SMBG systems were compared in a standardized manner under controlled laboratory conditions: nine systems were available on the German market and were purchased from a local pharmacy, and three systems were obtained from the manufacturer (two systems were available on the U.S. market, and one system was not yet introduced to the German market). System accuracy was evaluated following DIN EN ISO (International Organization for Standardization) 15197:2003. In addition, measurement reproducibility was assessed following a modified TNO (Netherlands Organization for Applied Scientific Research) procedure. Comparison measurements were performed with either the glucose oxidase method (YSI 2300 STAT Plus™ glucose analyzer; YSI Life Sciences, Yellow Springs, OH) or the hexokinase method (cobas(...

Research paper thumbnail of Performance evaluation of three continuous glucose monitoring systems: comparison of six sensors per subject in parallel

Journal of diabetes science and technology, 2013

This study is aimed at comparing the performance of three continuous glucose monitoring (CGM) sys... more This study is aimed at comparing the performance of three continuous glucose monitoring (CGM) systems following the Clinical and Laboratory Standards Institute's POCT05-A guideline, which provides recommendations for performance evaluation of CGM systems. A total of 12 subjects with type 1 diabetes were enrolled in this study. Each subject wore six CGM systems in parallel, two sensors of each CGM system [FreeStyle Navigator™ (Navigator), MiniMed Guardian® REAL-Time with Enlite sensor (Guardian), DexCom™ Seven® Plus 3rd generation (Seven Plus)]. Each sensor was used for the lifetime specified by the manufacturer. To follow POCT05-A recommendations, glucose excursions were induced on two separate occasions, and venous and capillary blood glucose (BG) concentrations were obtained every 15 min for five consecutive hours. Capillary BG concentrations were measured at least once per hour during the day and once at night. Parameters investigated were CGM-to-BG differences [mean absolute...

Research paper thumbnail of Performance evaluation of a continuous glucose monitoring system under conditions similar to daily life

Journal of diabetes science and technology, 2013

This study aimed at evaluating and comparing the performance of a new generation of continuous gl... more This study aimed at evaluating and comparing the performance of a new generation of continuous glucose monitoring (CGM) system versus other CGM systems, under daily lifelike conditions. A total of 10 subjects (7 female) were enrolled in this study. Each subject wore two Dexcom G4™ CGM systems in parallel for the sensor lifetime specified by the manufacturer (7 days) to allow assessment of sensor-to-sensor precision. Capillary blood glucose (BG) measurements were performed at least once per hour during daytime and once at night. Glucose excursions were induced on two occasions. Performance was assessed by calculating the mean absolute relative difference (MARD) between CGM readings and paired capillary BG readings and precision absolute relative difference (PARD), i.e., differences between paired CGM readings. Overall aggregate MARD was 11.0% (n = 2392). Aggregate MARD for BG <70 mg/dl was 13.7%; for BG between 70 and 180 mg/dl, MARD was 11.4%; and for BG >180 mg/dl, MARD was 8...