The Experts below are selected from a list of 14433 Experts worldwide ranked by ideXlab platform
Armando Tripodi - One of the best experts on this subject based on the ideXlab platform.
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point of care coagulation monitors calibrated for the international normalized ratio for cirrhosis inrliver can help to implement the inrliver for the calculation of the meld score
Journal of Hepatology, 2009Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, A Dellera, Marigrazia Clerici, F Iannuzzi, Alessio Aghemo, M Cazzaniga, Francesco Salerno, Pier Mannuccio MannucciAbstract:Background/Aims The MELD defines a score used to prioritize patients awaiting liver transplantation and includes results for bilirubin, creatinine and PT expressed as INR. It is assumed that the MELD for individual patients is the same regardless of the laboratory method used for testing, thus ensuring parity of organ allocation. Previous studies showed that the INR calibrated for patients on vitamin K antagonists (INR vka ) does not normalize results across Thromboplastins, whereas an alternative calibration called INR liver does. However, implementation of INR liver calibration for Thromboplastins is difficult in practice. This study aimed to assess whether easy-to-run whole-blood coagulation monitors (widely used for patients on VKA) can be calibrated to measure efficiently the INR liver and minimize the interlaboratory variability. Methods PT values for 61 cirrhotic patients were measured on native-blood with 2 monitors calibrated in terms of INR vka . PTs for these subjects were also measured with a WHO-standard for Thromboplastin. Paired-PTs with the monitors and the standard were subsequently used to calibrate the monitors in terms of INR liver . INR vka and INR liver were then compared to assess for statistical significance. Results The mean INR vka obtained with the monitors and the standard were significantly different ( p liver were not. Conclusions The INR liver calibration as previously described for Thromboplastins works also for the easy-to-run whole-blood coagulation monitors. Once the monitors are calibrated by the manufacturer in terms of INR liver they could be used as near-patient-testing devices directly by the personnel of liver units making the determination of the INR for patients awaiting liver transplantation much easier and standardized.
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the international normalized ratio calibrated for cirrhosis inrliver normalizes prothrombin time results for model for end stage liver disease calculation
Hepatology, 2007Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, Federica Fabris, A Dellera, Cinzia Sei, Pier Mannuccio MannucciAbstract:The model for end-stage-liver-disease (MELD) is a mathematical score used to prioritize patients for liver transplantation and includes results for creatinine, bilirubin, and prothrombin time (PT) expressed as international normalized ratio (INR). The rationale of using the MELD rests on the assumption that the score would be the same across the country if the methods used to measure the variables yield the same numerical results regardless of the testing laboratory. Evidence was provided that specific methodologies may influence the MELD, and the PT-INR was identified as the most important. This study was designed to provide information on the between-Thromboplastin variability and to explore alternatives to obviate such variability. Fifty-seven patients with cirrhosis were selected, and their PTs were measured with 7 Thromboplastins. The Thromboplastins were previously calibrated by testing plasmas from patients on vitamin K antagonists and healthy subjects to assign the international sensitivity index (ISIvka) needed to convert PT into INR. Each of the Thromboplastins was also assigned an ISIliver by substituting in the calibration the plasmas from vitamin K antagonist patients with plasmas from patients with cirrhosis. INR and MELD values for individual patients were calculated by using the ISIvka or the ISIliver. The mean INRvka obtained with the 7 Thromboplastins were significantly different (P < 0.001). Conversely, the mean INRliver were not. Similarly, the mean MELDvka were significantly different (P < 0.001), but those differences were abrogated for the MELDliver. Conclusion: The alternative Thromboplastin calibration using plasmas from patients with cirrhosis instead of from vitamin K antagonist patients is feasible and may resolve the variability of the MELD to prioritize patients for transplantation. (HEPATOLOGY 2007.)
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international collaborative study for the calibration of a proposed international standard for Thromboplastin rabbit plain
Journal of Thrombosis and Haemostasis, 2006Co-Authors: Veena Chantarangkul, A. M. H. P. Van Den Besselaar, E Witteveen, Armando TripodiAbstract:Summary. Background: A preparation of rabbit brain Thromboplastin, provisionally coded 04/162, is proposed as a candidate for the World Health Organization (WHO) International Standard (IS) for Thromboplastin (rabbit, plain), meant to replace the IS coded RBT/90 (rabbit, plain), stocks of which are now exhausted. Results: The preparation was calibrated in an international collaborative study involving 21 laboratories from 13 countries and the calibration was performed against the existing WHO-IS (i.e. rTF/95 and OBT/79) and other Certified Reference Materials from the Institute for Reference Materials and Measurements of the European Commission (i.e. CRM149 S) and from the European Action on Anticoagulation (i.e. EUTHR-01). An additional candidate rabbit brain Thromboplastin coded as 04/106 was also included in the study. On the basis of predefined criteria (the within- and between-laboratory precision of the calibration and the conformity to the calibration model), 04/162 was the preferred candidate. Conclusions: The assigned International Sensitivity Index value was 1.15 and the inter-laboratory SD and coefficient of variation were 0.057% and 4.9%, respectively.
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laboratory control of oral anticoagulant treatment by the inr system in patients with the antiphospholipid syndrome and lupus anticoagulant results of a collaborative study involving nine commercial Thromboplastins
British Journal of Haematology, 2001Co-Authors: Armando Tripodi, Veena Chantarangkul, Marigrazia Clerici, Barbara Negri, Monica Galli, Pier Mannuccio MannucciAbstract:Because of the variable responsiveness of Thromboplastins to lupus anticoagulants (LA), concerns have been raised about the validity of the prothrombin time–International Normalized Ratio (PT–INR) in monitoring oral anticoagulant treatment in patients with the antiphospholipid syndrome (APS) and LA. To date, few studies have been performed, numbers of patients investigated are relatively small and results are conflicting. We report on a multicentre study organized to investigate further this clinically relevant issue. Each of nine thrombosis centres was asked to collect plasma samples from patients with APS who were on oral anticoagulants (cases) and patients without APS who were on oral anticoagulants (controls). Nine Thromboplastins (three human recombinant, one from human placenta and five from rabbit brain) were calibrated at the co-ordinating centre according to World Health Organization guidelines. Measurements of the INR and factor X amidolytic activity for all frozen plasmas were performed centrally. The numbers of patients investigated were 58 cases and 57 controls. Between-reagent variability of the INR was higher in cases [coefficient of variation (CV) = 12·4%] than in controls (CV = 6·7%), but this was because of one of the Thromboplastins only (Thromborel R, human recombinant), which measured considerably higher INR values than the others in cases but not in controls. In conclusion, our data indicate that LA interference on the PT–INR measured with the majority of commercial Thromboplastins is not enough to cause concern if insensitive Thromboplastins, properly calibrated to assign them an instrument-specific International Sensitivity Index are used. New Thromboplastins, especially those made of relipidated tissue factor, should be checked for their responsiveness to LA before they are used to monitor oral anticoagulant treatment in patients with APS.
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are capillary whole blood coagulation monitors suitable for the control of oral anticoagulant treatment by the international normalized ratio
Thrombosis and Haemostasis, 1993Co-Authors: Armando Tripodi, Veena Chantarangkul, Arnaldo Arbini, Donato Bettega, Pier Mannuccio MannucciAbstract:The 512 Coagulation Monitor is a portable coagulation photometer that uses disposable cartridges containing a lyophilized rabbit brain Thromboplastin to measure the PT for capillary whole blood. It has been proposed as a suitable system for patient self monitoring at home, but its performance has never been thoroughly assessed for results expressed as International Normalized Ratio (INR). In particular, there is no available information about the adequacy of the WHO calibration model with the Monitor. The aims of the study were to determine the International Sensitivity Index (ISI) against the secondary International Reference Preparation for rabbit Thromboplastin and to assess the precision of the INR. The study demonstrates that the Monitor can be calibrated with the WHO model, because log-transformed PTs for patients stabilized on oral anticoagulants and normal individuals are linearly related and because the same orthogonal regression line describes patient and normal data points adequately. However, the ISI calculated in this study (2.715) is higher than that adopted by the manufacturer (2.036). The between-assay reproducibility of the Monitor is acceptable (CV = 9.7%) with results expressed in seconds, but become unacceptably poor when the results are converted into INR (CV = 18.8%) because of the high ISI value of the Thromboplastin used. We think that the Monitor might be suitable for monitoring oral anticoagulant therapy if the manufacturer would provide a more sensitive Thromboplastin in the cartridges.
Pier Mannuccio Mannucci - One of the best experts on this subject based on the ideXlab platform.
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point of care coagulation monitors calibrated for the international normalized ratio for cirrhosis inrliver can help to implement the inrliver for the calculation of the meld score
Journal of Hepatology, 2009Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, A Dellera, Marigrazia Clerici, F Iannuzzi, Alessio Aghemo, M Cazzaniga, Francesco Salerno, Pier Mannuccio MannucciAbstract:Background/Aims The MELD defines a score used to prioritize patients awaiting liver transplantation and includes results for bilirubin, creatinine and PT expressed as INR. It is assumed that the MELD for individual patients is the same regardless of the laboratory method used for testing, thus ensuring parity of organ allocation. Previous studies showed that the INR calibrated for patients on vitamin K antagonists (INR vka ) does not normalize results across Thromboplastins, whereas an alternative calibration called INR liver does. However, implementation of INR liver calibration for Thromboplastins is difficult in practice. This study aimed to assess whether easy-to-run whole-blood coagulation monitors (widely used for patients on VKA) can be calibrated to measure efficiently the INR liver and minimize the interlaboratory variability. Methods PT values for 61 cirrhotic patients were measured on native-blood with 2 monitors calibrated in terms of INR vka . PTs for these subjects were also measured with a WHO-standard for Thromboplastin. Paired-PTs with the monitors and the standard were subsequently used to calibrate the monitors in terms of INR liver . INR vka and INR liver were then compared to assess for statistical significance. Results The mean INR vka obtained with the monitors and the standard were significantly different ( p liver were not. Conclusions The INR liver calibration as previously described for Thromboplastins works also for the easy-to-run whole-blood coagulation monitors. Once the monitors are calibrated by the manufacturer in terms of INR liver they could be used as near-patient-testing devices directly by the personnel of liver units making the determination of the INR for patients awaiting liver transplantation much easier and standardized.
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the international normalized ratio calibrated for cirrhosis inrliver normalizes prothrombin time results for model for end stage liver disease calculation
Hepatology, 2007Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, Federica Fabris, A Dellera, Cinzia Sei, Pier Mannuccio MannucciAbstract:The model for end-stage-liver-disease (MELD) is a mathematical score used to prioritize patients for liver transplantation and includes results for creatinine, bilirubin, and prothrombin time (PT) expressed as international normalized ratio (INR). The rationale of using the MELD rests on the assumption that the score would be the same across the country if the methods used to measure the variables yield the same numerical results regardless of the testing laboratory. Evidence was provided that specific methodologies may influence the MELD, and the PT-INR was identified as the most important. This study was designed to provide information on the between-Thromboplastin variability and to explore alternatives to obviate such variability. Fifty-seven patients with cirrhosis were selected, and their PTs were measured with 7 Thromboplastins. The Thromboplastins were previously calibrated by testing plasmas from patients on vitamin K antagonists and healthy subjects to assign the international sensitivity index (ISIvka) needed to convert PT into INR. Each of the Thromboplastins was also assigned an ISIliver by substituting in the calibration the plasmas from vitamin K antagonist patients with plasmas from patients with cirrhosis. INR and MELD values for individual patients were calculated by using the ISIvka or the ISIliver. The mean INRvka obtained with the 7 Thromboplastins were significantly different (P < 0.001). Conversely, the mean INRliver were not. Similarly, the mean MELDvka were significantly different (P < 0.001), but those differences were abrogated for the MELDliver. Conclusion: The alternative Thromboplastin calibration using plasmas from patients with cirrhosis instead of from vitamin K antagonist patients is feasible and may resolve the variability of the MELD to prioritize patients for transplantation. (HEPATOLOGY 2007.)
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laboratory control of oral anticoagulant treatment by the inr system in patients with the antiphospholipid syndrome and lupus anticoagulant results of a collaborative study involving nine commercial Thromboplastins
British Journal of Haematology, 2001Co-Authors: Armando Tripodi, Veena Chantarangkul, Marigrazia Clerici, Barbara Negri, Monica Galli, Pier Mannuccio MannucciAbstract:Because of the variable responsiveness of Thromboplastins to lupus anticoagulants (LA), concerns have been raised about the validity of the prothrombin time–International Normalized Ratio (PT–INR) in monitoring oral anticoagulant treatment in patients with the antiphospholipid syndrome (APS) and LA. To date, few studies have been performed, numbers of patients investigated are relatively small and results are conflicting. We report on a multicentre study organized to investigate further this clinically relevant issue. Each of nine thrombosis centres was asked to collect plasma samples from patients with APS who were on oral anticoagulants (cases) and patients without APS who were on oral anticoagulants (controls). Nine Thromboplastins (three human recombinant, one from human placenta and five from rabbit brain) were calibrated at the co-ordinating centre according to World Health Organization guidelines. Measurements of the INR and factor X amidolytic activity for all frozen plasmas were performed centrally. The numbers of patients investigated were 58 cases and 57 controls. Between-reagent variability of the INR was higher in cases [coefficient of variation (CV) = 12·4%] than in controls (CV = 6·7%), but this was because of one of the Thromboplastins only (Thromborel R, human recombinant), which measured considerably higher INR values than the others in cases but not in controls. In conclusion, our data indicate that LA interference on the PT–INR measured with the majority of commercial Thromboplastins is not enough to cause concern if insensitive Thromboplastins, properly calibrated to assign them an instrument-specific International Sensitivity Index are used. New Thromboplastins, especially those made of relipidated tissue factor, should be checked for their responsiveness to LA before they are used to monitor oral anticoagulant treatment in patients with APS.
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are capillary whole blood coagulation monitors suitable for the control of oral anticoagulant treatment by the international normalized ratio
Thrombosis and Haemostasis, 1993Co-Authors: Armando Tripodi, Veena Chantarangkul, Arnaldo Arbini, Donato Bettega, Pier Mannuccio MannucciAbstract:The 512 Coagulation Monitor is a portable coagulation photometer that uses disposable cartridges containing a lyophilized rabbit brain Thromboplastin to measure the PT for capillary whole blood. It has been proposed as a suitable system for patient self monitoring at home, but its performance has never been thoroughly assessed for results expressed as International Normalized Ratio (INR). In particular, there is no available information about the adequacy of the WHO calibration model with the Monitor. The aims of the study were to determine the International Sensitivity Index (ISI) against the secondary International Reference Preparation for rabbit Thromboplastin and to assess the precision of the INR. The study demonstrates that the Monitor can be calibrated with the WHO model, because log-transformed PTs for patients stabilized on oral anticoagulants and normal individuals are linearly related and because the same orthogonal regression line describes patient and normal data points adequately. However, the ISI calculated in this study (2.715) is higher than that adopted by the manufacturer (2.036). The between-assay reproducibility of the Monitor is acceptable (CV = 9.7%) with results expressed in seconds, but become unacceptably poor when the results are converted into INR (CV = 18.8%) because of the high ISI value of the Thromboplastin used. We think that the Monitor might be suitable for monitoring oral anticoagulant therapy if the manufacturer would provide a more sensitive Thromboplastin in the cartridges.
Veena Chantarangkul - One of the best experts on this subject based on the ideXlab platform.
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point of care coagulation monitors calibrated for the international normalized ratio for cirrhosis inrliver can help to implement the inrliver for the calculation of the meld score
Journal of Hepatology, 2009Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, A Dellera, Marigrazia Clerici, F Iannuzzi, Alessio Aghemo, M Cazzaniga, Francesco Salerno, Pier Mannuccio MannucciAbstract:Background/Aims The MELD defines a score used to prioritize patients awaiting liver transplantation and includes results for bilirubin, creatinine and PT expressed as INR. It is assumed that the MELD for individual patients is the same regardless of the laboratory method used for testing, thus ensuring parity of organ allocation. Previous studies showed that the INR calibrated for patients on vitamin K antagonists (INR vka ) does not normalize results across Thromboplastins, whereas an alternative calibration called INR liver does. However, implementation of INR liver calibration for Thromboplastins is difficult in practice. This study aimed to assess whether easy-to-run whole-blood coagulation monitors (widely used for patients on VKA) can be calibrated to measure efficiently the INR liver and minimize the interlaboratory variability. Methods PT values for 61 cirrhotic patients were measured on native-blood with 2 monitors calibrated in terms of INR vka . PTs for these subjects were also measured with a WHO-standard for Thromboplastin. Paired-PTs with the monitors and the standard were subsequently used to calibrate the monitors in terms of INR liver . INR vka and INR liver were then compared to assess for statistical significance. Results The mean INR vka obtained with the monitors and the standard were significantly different ( p liver were not. Conclusions The INR liver calibration as previously described for Thromboplastins works also for the easy-to-run whole-blood coagulation monitors. Once the monitors are calibrated by the manufacturer in terms of INR liver they could be used as near-patient-testing devices directly by the personnel of liver units making the determination of the INR for patients awaiting liver transplantation much easier and standardized.
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the international normalized ratio calibrated for cirrhosis inrliver normalizes prothrombin time results for model for end stage liver disease calculation
Hepatology, 2007Co-Authors: Armando Tripodi, Veena Chantarangkul, Massimo Primignani, Federica Fabris, A Dellera, Cinzia Sei, Pier Mannuccio MannucciAbstract:The model for end-stage-liver-disease (MELD) is a mathematical score used to prioritize patients for liver transplantation and includes results for creatinine, bilirubin, and prothrombin time (PT) expressed as international normalized ratio (INR). The rationale of using the MELD rests on the assumption that the score would be the same across the country if the methods used to measure the variables yield the same numerical results regardless of the testing laboratory. Evidence was provided that specific methodologies may influence the MELD, and the PT-INR was identified as the most important. This study was designed to provide information on the between-Thromboplastin variability and to explore alternatives to obviate such variability. Fifty-seven patients with cirrhosis were selected, and their PTs were measured with 7 Thromboplastins. The Thromboplastins were previously calibrated by testing plasmas from patients on vitamin K antagonists and healthy subjects to assign the international sensitivity index (ISIvka) needed to convert PT into INR. Each of the Thromboplastins was also assigned an ISIliver by substituting in the calibration the plasmas from vitamin K antagonist patients with plasmas from patients with cirrhosis. INR and MELD values for individual patients were calculated by using the ISIvka or the ISIliver. The mean INRvka obtained with the 7 Thromboplastins were significantly different (P < 0.001). Conversely, the mean INRliver were not. Similarly, the mean MELDvka were significantly different (P < 0.001), but those differences were abrogated for the MELDliver. Conclusion: The alternative Thromboplastin calibration using plasmas from patients with cirrhosis instead of from vitamin K antagonist patients is feasible and may resolve the variability of the MELD to prioritize patients for transplantation. (HEPATOLOGY 2007.)
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international collaborative study for the calibration of a proposed international standard for Thromboplastin rabbit plain
Journal of Thrombosis and Haemostasis, 2006Co-Authors: Veena Chantarangkul, A. M. H. P. Van Den Besselaar, E Witteveen, Armando TripodiAbstract:Summary. Background: A preparation of rabbit brain Thromboplastin, provisionally coded 04/162, is proposed as a candidate for the World Health Organization (WHO) International Standard (IS) for Thromboplastin (rabbit, plain), meant to replace the IS coded RBT/90 (rabbit, plain), stocks of which are now exhausted. Results: The preparation was calibrated in an international collaborative study involving 21 laboratories from 13 countries and the calibration was performed against the existing WHO-IS (i.e. rTF/95 and OBT/79) and other Certified Reference Materials from the Institute for Reference Materials and Measurements of the European Commission (i.e. CRM149 S) and from the European Action on Anticoagulation (i.e. EUTHR-01). An additional candidate rabbit brain Thromboplastin coded as 04/106 was also included in the study. On the basis of predefined criteria (the within- and between-laboratory precision of the calibration and the conformity to the calibration model), 04/162 was the preferred candidate. Conclusions: The assigned International Sensitivity Index value was 1.15 and the inter-laboratory SD and coefficient of variation were 0.057% and 4.9%, respectively.
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laboratory control of oral anticoagulant treatment by the inr system in patients with the antiphospholipid syndrome and lupus anticoagulant results of a collaborative study involving nine commercial Thromboplastins
British Journal of Haematology, 2001Co-Authors: Armando Tripodi, Veena Chantarangkul, Marigrazia Clerici, Barbara Negri, Monica Galli, Pier Mannuccio MannucciAbstract:Because of the variable responsiveness of Thromboplastins to lupus anticoagulants (LA), concerns have been raised about the validity of the prothrombin time–International Normalized Ratio (PT–INR) in monitoring oral anticoagulant treatment in patients with the antiphospholipid syndrome (APS) and LA. To date, few studies have been performed, numbers of patients investigated are relatively small and results are conflicting. We report on a multicentre study organized to investigate further this clinically relevant issue. Each of nine thrombosis centres was asked to collect plasma samples from patients with APS who were on oral anticoagulants (cases) and patients without APS who were on oral anticoagulants (controls). Nine Thromboplastins (three human recombinant, one from human placenta and five from rabbit brain) were calibrated at the co-ordinating centre according to World Health Organization guidelines. Measurements of the INR and factor X amidolytic activity for all frozen plasmas were performed centrally. The numbers of patients investigated were 58 cases and 57 controls. Between-reagent variability of the INR was higher in cases [coefficient of variation (CV) = 12·4%] than in controls (CV = 6·7%), but this was because of one of the Thromboplastins only (Thromborel R, human recombinant), which measured considerably higher INR values than the others in cases but not in controls. In conclusion, our data indicate that LA interference on the PT–INR measured with the majority of commercial Thromboplastins is not enough to cause concern if insensitive Thromboplastins, properly calibrated to assign them an instrument-specific International Sensitivity Index are used. New Thromboplastins, especially those made of relipidated tissue factor, should be checked for their responsiveness to LA before they are used to monitor oral anticoagulant treatment in patients with APS.
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are capillary whole blood coagulation monitors suitable for the control of oral anticoagulant treatment by the international normalized ratio
Thrombosis and Haemostasis, 1993Co-Authors: Armando Tripodi, Veena Chantarangkul, Arnaldo Arbini, Donato Bettega, Pier Mannuccio MannucciAbstract:The 512 Coagulation Monitor is a portable coagulation photometer that uses disposable cartridges containing a lyophilized rabbit brain Thromboplastin to measure the PT for capillary whole blood. It has been proposed as a suitable system for patient self monitoring at home, but its performance has never been thoroughly assessed for results expressed as International Normalized Ratio (INR). In particular, there is no available information about the adequacy of the WHO calibration model with the Monitor. The aims of the study were to determine the International Sensitivity Index (ISI) against the secondary International Reference Preparation for rabbit Thromboplastin and to assess the precision of the INR. The study demonstrates that the Monitor can be calibrated with the WHO model, because log-transformed PTs for patients stabilized on oral anticoagulants and normal individuals are linearly related and because the same orthogonal regression line describes patient and normal data points adequately. However, the ISI calculated in this study (2.715) is higher than that adopted by the manufacturer (2.036). The between-assay reproducibility of the Monitor is acceptable (CV = 9.7%) with results expressed in seconds, but become unacceptably poor when the results are converted into INR (CV = 18.8%) because of the high ISI value of the Thromboplastin used. We think that the Monitor might be suitable for monitoring oral anticoagulant therapy if the manufacturer would provide a more sensitive Thromboplastin in the cartridges.
L Poller - One of the best experts on this subject based on the ideXlab platform.
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the prothrombin time international normalized ratio pt inr line derivation of local inr with commercial Thromboplastins and coagulometers two independent studies
Journal of Thrombosis and Haemostasis, 2011Co-Authors: L Poller, Saied Ibrahim, M Keown, Albert Pattison, J JespersenAbstract:Summary. Background: The WHO scheme for prothrombin time (PT) standardization has been limited in application, because of its difficulties in implementation, particularly the need for mandatory manual PT testing and for local provision of Thromboplastin international reference preparations (IRP). Methods: The value of a new simpler procedure to derive international normalized ratio (INR), the PT/INR Line, based on only five European Concerted Action on Anticoagulation (ECAA) calibrant plasmas certified by experienced centres has been assessed in two independent exercises using a range of commercial Thromboplastins and coagulometers. INRs were compared with manual certified values with Thromboplastin IRP from expert centres and in the second study also with INRs from local ISI calibrations. Results: In the first study with the PT/INR Line, 8.7% deviation from certified INRs was reduced to 1.1% with human reagents, and from 7.0% to 2.6% with rabbit reagents. In the second study, deviation was reduced from 11.2% to 0.4% with human reagents by both local ISI calibration and the PT/INR Line. With rabbit reagents, 10.4% deviation was reduced to 1.1% with both procedures; 4.9% deviation was reduced to 0.5% with bovine/combined reagents with local ISI calibrations and to 2.9% with the PT/INR Line. Mean INR dispersion was reduced with all Thromboplastins and automated systems using the PT/INR Line. Conclusions: The procedure using the PT/INR Line provides reliable INR derivation without the need for WHO ISI calibration across the range of locally used commercial Thromboplastins and automated PT systems included in two independent international studies.
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simplified method for international normalized ratio inr derivation based on the prothrombin time inr line an international study
Clinical Chemistry, 2010Co-Authors: L Poller, Saied Ibrahim, M Keown, Albert Pattison, J JespersenAbstract:BACKGROUND: The need to perform local International Sensitivity Index (ISI) calibrations and in particular the requirement for a manual method for prothrombin time (PT)determination,haveprovedtobeobstaclestoapplication of the WHO scheme for PT standardization. METHODS: We used international normalized ratio (INR) derived with a set of only 5 European Concerted Action on Anticoagulation (ECAA) lyophilized calibrant plasmas, certified manually by expert centers with reference Thromboplastins, to determine a local PT/INR Line. We compared results of an independent set of validation plasmas with INRs from conventional ISI calibrations and with manually certified INRs. RESULTS: The mean certified INR of 5 lyophilized validation plasmas was 2.41 with human Thromboplastin, 2.04withbovine/combined,and2.80withrabbit.With 42 human reagents, the mean observed INR of the validation plasmas was 2.68 (11.2% deviation from certified INR). Deviation was reduced to 0.4% with both local ISI calibration and the PT/INR Line. Eight results based on bovine/combined Thromboplastin gave an INR deviation of 4.9%, becoming 0.5% after ISI calibration and 2.4% with the PT/INR Line. Six results with rabbit reagents deviated from certified INR by 2.5%. After ISI calibration, deviation became 1.1%, and with the PT/INR Line, 0.7%. The PT/INR Line gave similar results with both linear and orthogonal regression analysis. The total proportion of validation plasmas giving INR within 10% deviation from certified values was 42.5% with uncorrected INR, which increasedto92.1%withlocalISIcalibrationand93.2% with the PT/INR Line. CONCLUSIONS: The PT/INR Line procedure with 5 ECAA calibrant plasmas successfully substitutes for local ISI calibrations in deriving reliable INRs. © 2010 American Association for Clinical Chemistry
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the european concerted action on anticoagulation ecaa field studies of coagulometer effects on the isi of ecaa Thromboplastins
Thrombosis and Haemostasis, 1998Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, J Jespersen, A Tripodi, D HoughtonAbstract:Local calibration studies have been performed with lyophilized plasmas at 155 European laboratories to assess coagulometer effects on manual ISI of ECAA Thromboplastins (low ISI human recombinant and high ISI rabbit brain). Common sets of 7 normal and 20 artificially depleted lyophilized plasmas were tested with the Thromboplastins in the routine local coagulometers. With the human reagent, marked lowering of the manual ISI resulted with most coagulometers, which was associated with disproportionate shortening of the normals. Where this shortening did not occur, there was little coagulometer effect on the ISI. With the rabbit reagent, proportionate shortening with both normal and abnormal plasmas occurred in most instruments with little effect on ISI. INR correction by local ISI assignment appeared successful with the ECAA human reagent. There was negligible INR correction from local calibration of the ECAA rabbit reagent in coagulometers where Thromboplastin ISI were unchanged from the ECAA established manual values.
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the european concerted action on anticoagulation ecaa evaluation of a set of lyophilized normal plasmas to establish the normal prothrombin time for coagulometer systems
Thrombosis and Haemostasis, 1998Co-Authors: L Poller, A. M. H. P. Van Den Besselaar, J Jespersen, A Tripodi, T W Barrowcliffe, D HoughtonAbstract:Establishing the mean normal prothrombin time (MNPT) from fresh samples for prothrombin ratios and INR often presents difficulty in selection and collection of donors. A set of seven lyophilized normal plasmas has therefore been prepared at the ECAA Central Facility and studied at 143 laboratories in sixteen European states using coagulometers in serial field exercises. All centres tested either the high ISI ECAA rabbit or low ISI ECAA human reference Thromboplastin. The MNPT of fresh plasmas and means of the lyophilized samples were closely comparable with most routine rabbit Thromboplastins. Using human Thromboplastins means with the lyophilized normals were marginally but significantly longer and with the bovine Thrombotest significantly shorter than the MNPT of fresh plasmas causing alterations in INR. There was no appreciable effect on INR of 2.5 and 3.5 when lyophilized normals were substituted for fresh normals with the rabbit reagents.
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a comparison of lyophilized artificially depleted plasmas and lyophilized plasmas from patients receiving warfarin in correcting for coagulometer effects on international normalized ratios
American Journal of Clinical Pathology, 1995Co-Authors: L Poller, Jack Hirsh, Douglas A Triplett, J J Carroll, K ClarkeAbstract:The comparative value of lyophilized artificially depleted plasmas and plasmas from warfarin-treated patients in local (Thromboplastin/coagulometer) system International Sensitivity Indices (ISI) determination has been studied at 39 centers in an international collaborative study. At each center, both types of plasmas were tested with two common Thromboplastins (low ISI RecombiPlasTin and high ISI OBT), and in-house reagents using three brands of coagulometers. In 95 local systems, they was agreement. With both Thromboplastins, coagulometers lowered the ISI from the manual or stated ISI with all systems. Differences between the two types of lyophilized plasmas with the two common Thromboplastins were not of clinical importance. Artificially depleted plasmas are easier to obtain in sufficient volumes than plasma from warfarin-treated patients, and more easily provide the wide range of INR values required for reliable local ISI calibration. The agreement between the two types of lyophilized calibrant is reassuring.
Christa M Cobbaert - One of the best experts on this subject based on the ideXlab platform.
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a comparative study of conventional versus new magnesium poor vacutainer sodium citrate blood collection tubes for determination of prothrombin time and inr
Thrombosis Research, 2014Co-Authors: Anton M H P Van Den Besselaar, Iris J H Van Vlodrop, Paul Berendes, Christa M CobbaertAbstract:Abstract Introduction Conventional Vacutainer® Sodium Citrate blood collection tubes contain a relatively high concentration of contaminating magnesium ions, which may result in shortening of the prothrombin time (PT) and the International Normalized Ratio (INR). Recently the manufacturer of Vacutainer® Sodium Citrate tubes introduced new tubes with a magnesium-poor stopper. The magnesium concentration in the new low-Mg tubes is significantly lower than that in the conventional plastic tubes. The purpose of the present study was to compare PT and INR determined in specimens drawn with the new tubes to those drawn with the conventional tubes. Materials and Methods Venous blood specimens were collected from 22 healthy persons and 65 patients treated with vitamin K-antagonists using conventional Vacutainer® Sodium Citrate tubes and new, low-Mg Vacutainer® tubes. PT and INR were determined with four Thromboplastin reagents, i.e., three brands of recombinant human tissue factor and one brand of combined rabbit brain reagent. Magnesium concentrations were determined in the citrate plasmas with a colorimetric method. Results The differences in PT, INR and International Sensitivity Index (ISI) between the two tubes were significant when using three recombinant human Thromboplastin reagents, but were not significant when using the rabbit Thromboplastin. The PT and INR differences between the tubes correlated with the magnesium concentration differences ( P Conclusion Agreement of INR between reagents is improved by using magnesium-poor tubes.
