The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Justyna Golebiewska - One of the best experts on this subject based on the ideXlab platform.
-
assessment of simple indices based on a single fasting blood sample as a tool to estimate beta cell Function after total pancreatectomy with islet autotransplantation a prospective study
Transplant International, 2019Co-Authors: Justyna Golebiewska, Piotr J Bachul, Natalie Fillman, Lindsay Basto, Mark R Kijek, Karolina Goląb, Lingjia Wang, Martin TibudanAbstract:We investigated six indices based on a single fasting blood sample for evaluation of the beta-cell Function after total pancreatectomy with islet autotransplantation (TP-IAT). The Secretory Unit of Islet Transplant Objects (SUITO), transplant Estimated Function (TEF), homeostasis model assessment (HOMA-2B%), C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr) and BETA-2 score were compared against a 90-min serum glucose level, weighted mean C-peptide in mixed meal tolerance test (MMTT), beta score and the Igls score adjusted for islet Function in the setting of IAT. We analyzed values from 32 MMTTs in 15 patients after TP-IAT with a follow-up of up to 3 years. Four (27%) individuals had discontinued insulin completely prior to day 75, while 6 out of 12 patients (50%) did not require insulin support at 1-year follow-up with HbA1c 6.0% (5.5-6.8). BETA-2 was the most consistent among indices strongly correlating with all reference measures of beta-cell Function (r = 0.62-0.68). In addition, it identified insulin independence (cut-off = 16.2) and optimal/good versus marginal islet Function in the Igls score well, with AUROC of 0.85 and 0.96, respectively. Based on a single fasting blood sample, BETA-2 score has the most reliable discriminant value for the assessment of graft Function in patients undergoing TP-IAT.
-
comparative evaluation of simple indices using a single fasting blood sample to estimate beta cell Function after islet transplantation
American Journal of Transplantation, 2018Co-Authors: Justyna Golebiewska, Piotr J Bachul, Lindsay Basto, Mark R Kijek, Karolina Goląb, Julia Solomina, Celeste C Thomas, Lingjia WangAbstract:Six single fasting blood sample-based indices-Secretory Unit of Islet Transplant Objects (SUITO), Transplant Estimated Function (TEF), Homeostasis Model Assessment (HOMA)2-B%, C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr), and BETA-2 score-were compared against commonly used 90-minute mixed meal tolerance test (MMTT) serum glucose and beta score to assess which of them best recognizes the state of acceptable blood glucose control without insulin supplementation after islet allotransplantation (ITx). We also tested whether the indices could identify the success of ITx based on the Igls classification of beta cell graft Function. We analyzed values from 47 MMTT tests in 4 patients with up to 140 months follow-up and from 54 MMTT tests in 13 patients with up to 42 months follow-up. SUITO, CP/G, HOMA2-B%, and BETA-2 correlated well with the 90-minute glucose of the MMTT and beta-score (r 0.54-0.76), whereas CP/GCr showed a modest performance (r 0.41-0.52) while TEF showed little correlation. BETA-2 and SUITO were the best identifiers and predictors of the need for insulin support, glucose intolerance, and ITx success (P < .001), while HOMA2-B% and TEF were unreliable. Single fasting blood sample SUITO and BETA-2 scores are very practical alternative tools that allow for frequent assessments of graft Function.
Piotr J Bachul - One of the best experts on this subject based on the ideXlab platform.
-
assessment of simple indices based on a single fasting blood sample as a tool to estimate beta cell Function after total pancreatectomy with islet autotransplantation a prospective study
Transplant International, 2019Co-Authors: Justyna Golebiewska, Piotr J Bachul, Natalie Fillman, Lindsay Basto, Mark R Kijek, Karolina Goląb, Lingjia Wang, Martin TibudanAbstract:We investigated six indices based on a single fasting blood sample for evaluation of the beta-cell Function after total pancreatectomy with islet autotransplantation (TP-IAT). The Secretory Unit of Islet Transplant Objects (SUITO), transplant Estimated Function (TEF), homeostasis model assessment (HOMA-2B%), C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr) and BETA-2 score were compared against a 90-min serum glucose level, weighted mean C-peptide in mixed meal tolerance test (MMTT), beta score and the Igls score adjusted for islet Function in the setting of IAT. We analyzed values from 32 MMTTs in 15 patients after TP-IAT with a follow-up of up to 3 years. Four (27%) individuals had discontinued insulin completely prior to day 75, while 6 out of 12 patients (50%) did not require insulin support at 1-year follow-up with HbA1c 6.0% (5.5-6.8). BETA-2 was the most consistent among indices strongly correlating with all reference measures of beta-cell Function (r = 0.62-0.68). In addition, it identified insulin independence (cut-off = 16.2) and optimal/good versus marginal islet Function in the Igls score well, with AUROC of 0.85 and 0.96, respectively. Based on a single fasting blood sample, BETA-2 score has the most reliable discriminant value for the assessment of graft Function in patients undergoing TP-IAT.
-
comparative evaluation of simple indices using a single fasting blood sample to estimate beta cell Function after islet transplantation
American Journal of Transplantation, 2018Co-Authors: Justyna Golebiewska, Piotr J Bachul, Lindsay Basto, Mark R Kijek, Karolina Goląb, Julia Solomina, Celeste C Thomas, Lingjia WangAbstract:Six single fasting blood sample-based indices-Secretory Unit of Islet Transplant Objects (SUITO), Transplant Estimated Function (TEF), Homeostasis Model Assessment (HOMA)2-B%, C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr), and BETA-2 score-were compared against commonly used 90-minute mixed meal tolerance test (MMTT) serum glucose and beta score to assess which of them best recognizes the state of acceptable blood glucose control without insulin supplementation after islet allotransplantation (ITx). We also tested whether the indices could identify the success of ITx based on the Igls classification of beta cell graft Function. We analyzed values from 47 MMTT tests in 4 patients with up to 140 months follow-up and from 54 MMTT tests in 13 patients with up to 42 months follow-up. SUITO, CP/G, HOMA2-B%, and BETA-2 correlated well with the 90-minute glucose of the MMTT and beta-score (r 0.54-0.76), whereas CP/GCr showed a modest performance (r 0.41-0.52) while TEF showed little correlation. BETA-2 and SUITO were the best identifiers and predictors of the need for insulin support, glucose intolerance, and ITx success (P < .001), while HOMA2-B% and TEF were unreliable. Single fasting blood sample SUITO and BETA-2 scores are very practical alternative tools that allow for frequent assessments of graft Function.
Lingjia Wang - One of the best experts on this subject based on the ideXlab platform.
-
assessment of simple indices based on a single fasting blood sample as a tool to estimate beta cell Function after total pancreatectomy with islet autotransplantation a prospective study
Transplant International, 2019Co-Authors: Justyna Golebiewska, Piotr J Bachul, Natalie Fillman, Lindsay Basto, Mark R Kijek, Karolina Goląb, Lingjia Wang, Martin TibudanAbstract:We investigated six indices based on a single fasting blood sample for evaluation of the beta-cell Function after total pancreatectomy with islet autotransplantation (TP-IAT). The Secretory Unit of Islet Transplant Objects (SUITO), transplant Estimated Function (TEF), homeostasis model assessment (HOMA-2B%), C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr) and BETA-2 score were compared against a 90-min serum glucose level, weighted mean C-peptide in mixed meal tolerance test (MMTT), beta score and the Igls score adjusted for islet Function in the setting of IAT. We analyzed values from 32 MMTTs in 15 patients after TP-IAT with a follow-up of up to 3 years. Four (27%) individuals had discontinued insulin completely prior to day 75, while 6 out of 12 patients (50%) did not require insulin support at 1-year follow-up with HbA1c 6.0% (5.5-6.8). BETA-2 was the most consistent among indices strongly correlating with all reference measures of beta-cell Function (r = 0.62-0.68). In addition, it identified insulin independence (cut-off = 16.2) and optimal/good versus marginal islet Function in the Igls score well, with AUROC of 0.85 and 0.96, respectively. Based on a single fasting blood sample, BETA-2 score has the most reliable discriminant value for the assessment of graft Function in patients undergoing TP-IAT.
-
comparative evaluation of simple indices using a single fasting blood sample to estimate beta cell Function after islet transplantation
American Journal of Transplantation, 2018Co-Authors: Justyna Golebiewska, Piotr J Bachul, Lindsay Basto, Mark R Kijek, Karolina Goląb, Julia Solomina, Celeste C Thomas, Lingjia WangAbstract:Six single fasting blood sample-based indices-Secretory Unit of Islet Transplant Objects (SUITO), Transplant Estimated Function (TEF), Homeostasis Model Assessment (HOMA)2-B%, C-peptide/glucose ratio (CP/G), C-peptide/glucose creatinine ratio (CP/GCr), and BETA-2 score-were compared against commonly used 90-minute mixed meal tolerance test (MMTT) serum glucose and beta score to assess which of them best recognizes the state of acceptable blood glucose control without insulin supplementation after islet allotransplantation (ITx). We also tested whether the indices could identify the success of ITx based on the Igls classification of beta cell graft Function. We analyzed values from 47 MMTT tests in 4 patients with up to 140 months follow-up and from 54 MMTT tests in 13 patients with up to 42 months follow-up. SUITO, CP/G, HOMA2-B%, and BETA-2 correlated well with the 90-minute glucose of the MMTT and beta-score (r 0.54-0.76), whereas CP/GCr showed a modest performance (r 0.41-0.52) while TEF showed little correlation. BETA-2 and SUITO were the best identifiers and predictors of the need for insulin support, glucose intolerance, and ITx success (P < .001), while HOMA2-B% and TEF were unreliable. Single fasting blood sample SUITO and BETA-2 scores are very practical alternative tools that allow for frequent assessments of graft Function.
Gary D Ferrier - One of the best experts on this subject based on the ideXlab platform.
-
direction selection in stochastic directional distance Functions
European Journal of Operational Research, 2020Co-Authors: Kevin Layer, Andrew L Johnson, Robin C Sickles, Gary D FerrierAbstract:Researchers rely on the distance Function to model multiple product production using multiple inputs. A stochastic directional distance Function (SDDF) allows for noise in potentially all input and output variables, yet when Estimated, the direction selected will affect the Functional estimates because deviations from the Estimated Function are minimized in the specified direction. Specifically, the parameters of the parametric SDDF are point identified when the direction is specified; we show that the parameters of the parametric SDDF are set identified when multiple directions are considered. Further, the set of identified parameters can be narrowed via data-driven approaches to restrict the directions considered. We demonstrate a similar narrowing of the identified parameter set for a shape constrained nonparametric method, where the shape constraints impose standard features of a cost Function such as monotonicity and convexity. Our Monte Carlo simulation studies reveal significant improvements, as measured by out of sample radial mean squared error, in Functional estimates when we use a directional distance Function with an appropriately selected direction and the errors are uncorrelated across variables. We show that these benefits increase as the correlation in error terms across variables increases. This correlation is a type of endogeneity that is common in production settings. From our Monte Carlo simulations we conclude that selecting a direction that is approximately orthogonal to the Estimated Function in the central region of the data gives significantly better estimates relative to the directions commonly used in the literature. For practitioners, our results imply that selecting a direction vector that has non-zero components for all variables that may have measurement error provides a significant improvement in the estimator's performance. We illustrate these results using cost and production data from three random samples of approximately 500 US hospitals operating in 2007, 2008, and 2009, respectively, and find that the shape constrained nonparametric methods provide a significant increase in flexibility over second order local approximation parametric methods.
-
direction selection in stochastic directional distance Functions
arXiv: Applications, 2019Co-Authors: Kevin Layer, Andrew L Johnson, Robin C Sickles, Gary D FerrierAbstract:Researchers rely on the distance Function to model multiple product production using multiple inputs. A stochastic directional distance Function (SDDF) allows for noise in potentially all input and output variables. Yet, when Estimated, the direction selected will affect the Functional estimates because deviations from the Estimated Function are minimized in the specified direction. The set of identified parameters of a parametric SDDF can be narrowed via data-driven approaches to restrict the directions considered. We demonstrate a similar narrowing of the identified parameter set for a shape constrained nonparametric method, where the shape constraints impose standard features of a cost Function such as monotonicity and convexity. Our Monte Carlo simulation studies reveal significant improvements, as measured by out of sample radial mean squared error, in Functional estimates when we use a directional distance Function with an appropriately selected direction. From our Monte Carlo simulations we conclude that selecting a direction that is approximately orthogonal to the Estimated Function in the central region of the data gives significantly better estimates relative to the directions commonly used in the literature. For practitioners, our results imply that selecting a direction vector that has non-zero components for all variables that may have measurement error provides a significant improvement in the estimator's performance. We illustrate these results using cost and production data from samples of approximately 500 US hospitals per year operating in 2007, 2008, and 2009, respectively, and find that the shape constrained nonparametric methods provide a significant increase in flexibility over second order local approximation parametric methods.
Andrew L Johnson - One of the best experts on this subject based on the ideXlab platform.
-
direction selection in stochastic directional distance Functions
European Journal of Operational Research, 2020Co-Authors: Kevin Layer, Andrew L Johnson, Robin C Sickles, Gary D FerrierAbstract:Researchers rely on the distance Function to model multiple product production using multiple inputs. A stochastic directional distance Function (SDDF) allows for noise in potentially all input and output variables, yet when Estimated, the direction selected will affect the Functional estimates because deviations from the Estimated Function are minimized in the specified direction. Specifically, the parameters of the parametric SDDF are point identified when the direction is specified; we show that the parameters of the parametric SDDF are set identified when multiple directions are considered. Further, the set of identified parameters can be narrowed via data-driven approaches to restrict the directions considered. We demonstrate a similar narrowing of the identified parameter set for a shape constrained nonparametric method, where the shape constraints impose standard features of a cost Function such as monotonicity and convexity. Our Monte Carlo simulation studies reveal significant improvements, as measured by out of sample radial mean squared error, in Functional estimates when we use a directional distance Function with an appropriately selected direction and the errors are uncorrelated across variables. We show that these benefits increase as the correlation in error terms across variables increases. This correlation is a type of endogeneity that is common in production settings. From our Monte Carlo simulations we conclude that selecting a direction that is approximately orthogonal to the Estimated Function in the central region of the data gives significantly better estimates relative to the directions commonly used in the literature. For practitioners, our results imply that selecting a direction vector that has non-zero components for all variables that may have measurement error provides a significant improvement in the estimator's performance. We illustrate these results using cost and production data from three random samples of approximately 500 US hospitals operating in 2007, 2008, and 2009, respectively, and find that the shape constrained nonparametric methods provide a significant increase in flexibility over second order local approximation parametric methods.
-
direction selection in stochastic directional distance Functions
arXiv: Applications, 2019Co-Authors: Kevin Layer, Andrew L Johnson, Robin C Sickles, Gary D FerrierAbstract:Researchers rely on the distance Function to model multiple product production using multiple inputs. A stochastic directional distance Function (SDDF) allows for noise in potentially all input and output variables. Yet, when Estimated, the direction selected will affect the Functional estimates because deviations from the Estimated Function are minimized in the specified direction. The set of identified parameters of a parametric SDDF can be narrowed via data-driven approaches to restrict the directions considered. We demonstrate a similar narrowing of the identified parameter set for a shape constrained nonparametric method, where the shape constraints impose standard features of a cost Function such as monotonicity and convexity. Our Monte Carlo simulation studies reveal significant improvements, as measured by out of sample radial mean squared error, in Functional estimates when we use a directional distance Function with an appropriately selected direction. From our Monte Carlo simulations we conclude that selecting a direction that is approximately orthogonal to the Estimated Function in the central region of the data gives significantly better estimates relative to the directions commonly used in the literature. For practitioners, our results imply that selecting a direction vector that has non-zero components for all variables that may have measurement error provides a significant improvement in the estimator's performance. We illustrate these results using cost and production data from samples of approximately 500 US hospitals per year operating in 2007, 2008, and 2009, respectively, and find that the shape constrained nonparametric methods provide a significant increase in flexibility over second order local approximation parametric methods.