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Chandrashekar V. Simplified Method for Local Correction of System International Normalized Ratio. Lab Med 2017; 48:244-248. [PMID: 28934513 DOI: 10.1093/labmed/lmx028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Background International normalized ratio (INR) derivation is dependent on the international sensitivity index (ISI) of thromboplastin. It varies with instrument and reagents used. Objective To evaluate the role of a correction factor in the derivation of INR. Methods We studied prothrombin time (PT) and INR from patients using 3 thromboplastins of varying ISI values. The correction factor was applied to the observed INR to obtain a corrected INR. Results The difference between corrected INR and observed INR values varies from -0.8 through 0.96. Conclusions Corrected INR is dependent on PT only. It can be applied to all patients irrespective of cause for elevated PT.
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Nutescu EA, Burnett A, Fanikos J, Spinler S, Wittkowsky A. Erratum to: Pharmacology of anticoagulants used in the treatment of venous thromboembolism. J Thromb Thrombolysis 2016; 42:296-311. [PMID: 27145758 PMCID: PMC4969935 DOI: 10.1007/s11239-016-1363-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Anticoagulant drugs are the foundation of therapy for patients with VTE. While effective therapeutic agents, anticoagulants can also result in hemorrhage and other side effects. Thus, anticoagulant therapy selection should be guided by the risks, benefits and pharmacologic characteristics of each agent for each patient. Safe use of anticoagulants requires not only an in-depth knowledge of their pharmacologic properties but also a comprehensive approach to patient management and education. This paper will summarize the key pharmacologic properties of the anticoagulant agents used in the treatment of patients with VTE.
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Affiliation(s)
- Edith A Nutescu
- Department of Pharmacy Systems Outcomes and Policy and Center for Pharmacoepidemiology & Pharmacoeconomic Research, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA.
| | - Allison Burnett
- Inpatient Antithrombosis Services, University of New Mexico Hospital, University of New Mexico College of Pharmacy, Albuquerque, NM, USA
| | - John Fanikos
- Brigham and Women's Hospital, Massachusetts College of Pharmacy, Boston, MA, USA
| | - Sarah Spinler
- Philadelphia College of Pharmacy and Science, Philadelphia, PA, USA
| | - Ann Wittkowsky
- University of Washington School of Pharmacy, Seattle, WA, USA
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Poller L. European Concerted Action on Anticoagulation (ECAA): Clinical and Laboratory Studies. Hematology 2016; 3:321-32. [DOI: 10.1080/10245332.1998.11746405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- L. Poller
- Department of Pathological Sciences, The University of Manchester, Stopford Building, Oxford Road, Manchester M13 9PT, UK
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Nutescu EA, Burnett A, Fanikos J, Spinler S, Wittkowsky A. Pharmacology of anticoagulants used in the treatment of venous thromboembolism. J Thromb Thrombolysis 2016; 41:15-31. [PMID: 26780737 PMCID: PMC4715843 DOI: 10.1007/s11239-015-1314-3] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Anticoagulant drugs are the foundation of therapy for patients with VTE. While effective therapeutic agents, anticoagulants can also result in hemorrhage and other side effects. Thus, anticoagulant therapy selection should be guided by the risks, benefits and pharmacologic characteristics of each agent for each patient. Safe use of anticoagulants requires not only an in-depth knowledge of their pharmacologic properties but also a comprehensive approach to patient management and education. This paper will summarize the key pharmacologic properties of the anticoagulant agents used in the treatment of patients with VTE.
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Affiliation(s)
- Edith A Nutescu
- Department of Pharmacy Systems Outcomes and Policy and Center for Pharmacoepidemiology & Pharmacoeconomic Research, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA.
| | - Allison Burnett
- Inpatient Antithrombosis Services, University of New Mexico Hospital, University of New Mexico College of Pharmacy, Albuquerque, NM, USA
| | - John Fanikos
- Brigham and Women's Hospital, Massachusetts College of Pharmacy, Boston, MA, USA
| | - Sarah Spinler
- Philadelphia College of Pharmacy and Science, Philadelphia, PA, USA
| | - Ann Wittkowsky
- University of Washington School of Pharmacy, Seattle, WA, USA
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Lee HJ, Kim JE, Lee HY, Lim HS, Kim HK. Significance of local international sensitivity index systems for monitoring warfarin and liver function. Am J Clin Pathol 2014; 141:542-50. [PMID: 24619756 DOI: 10.1309/ajcp2ry1pirrpuow] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
OBJECTIVES Use of a local calibrator has been recommended for standardization of the international normalized ratio (INR) and international sensitivity index (ISI). We investigated the performance of two commercial local calibrators for warfarin monitoring and determined the significance of liver-specific INR. METHODS ISI values were determined using the World Health Organization (WHO) method and two commercial local calibrators. Liver-specific ISI was determined using plasma samples from patients with liver cirrhosis and normal controls. RESULTS In warfarin monitoring, the two local ISIs determined by the two local calibrators showed better consistency than uncorrected ISI, although they were inferior to the ISIs calibrated using the WHO method. Alternative calibration using calibration plasma from patients with liver cirrhosis instead of warfarinized plasma reduced the INR variability. CONCLUSIONS Local ISI determined by a commercial local calibrator improved INR standardization among thromboplastins. The alternative ISI calibration using liver-specific calibration plasma is expected to reduce INR variability for the evaluation of liver function.
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Affiliation(s)
- Hwa Jeen Lee
- Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Ji-Eun Kim
- Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea
| | - Hye Yeon Lee
- Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Hae Sook Lim
- Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea
| | - Hyun Kyung Kim
- Department of Laboratory Medicine, Seoul National University College of Medicine, Seoul, Korea
- Cancer Research Institute, Seoul National University College of Medicine, Seoul, Korea
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Use of INR calibrator plasmas in the routine coagulation laboratory: a study of two thrombolastin reagents. Thromb Res 2012; 130:e158-62. [PMID: 22682443 DOI: 10.1016/j.thromres.2012.05.015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 04/29/2012] [Accepted: 05/11/2012] [Indexed: 11/22/2022]
Abstract
INR values may be either calculated with the ISI values supplied by thromboplastin manufacturers or are directly extrapolated from certified INR calibrator plasmas. We tested the principle of local INR calibration using INR calibrator plasmas (PT-Multi Calibrator, Siemens), two thromboplastin reagents (Neoplastin Plus, rabbit brain, Stago, coagulometer-specific ISI 1.31, and Innovin, recombinant human tissue factor, Siemens) and the same coagulometer (STA-R, Stago) in 100 patients on warfarin. Using a ISI value of 0.77 with Tomenson correction for Innovin (correction factor=1.09), INR values of patients were similar with the two reagents, with a bias of 0.03 INR units and no significant regression of the difference over the average INR by method comparison analysis. With the INR calibrator plasmas, INR values with Neoplastin Plus were lower than Innovin values with an average bias of 0.39 INR units and a significant regression of the difference over the average INR (r=-0.91). Significant bias (0.16 INR units, p<0.00001) and regression (r=-0.77) was also observed by comparison of Neoplastin Plus INRs with Innovin calibrated INRs. Based on a therapeutic INR interval of 2.0 to 3.5, discordance in warfarin dosing was approximately 3 times higher with INR calibration (27% vs 11%). Because of non commutability with fresh plasma samples, local INR calibration with lyophilized calibrator plasmas may not be valid for some reagent-instrument combinations.
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Poller L, Jespersen J, Ibrahim S. Artificially depleted plasmas are not necessarily commutable with native patient plasmas for International Sensitivity Index calibration and International Normalized Ratio derivation: a rebuttal. J Thromb Haemost 2012; 10:1197-8; author reply 1198-200. [PMID: 22487169 DOI: 10.1111/j.1538-7836.2012.04731.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
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VAN DEN BESSELAAR AMHP. Artificially depleted plasmas are not necessarily commutable with native patient plasmas for International Sensitivity Index calibration and International Normalized Ratio derivation: a reply to a rebuttal. J Thromb Haemost 2012. [DOI: 10.1111/j.1538-7836.2012.04730.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Budak YU, Huysal K, Polat M, Tarakçi G, Uçar H. Evaluation of the Steelex M600H coagulometer prothrombin time-international normalized ratio assay with Steelex test reagents. Biochem Med (Zagreb) 2012; 22:121-6. [PMID: 22384527 PMCID: PMC4062317 DOI: 10.11613/bm.2012.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 12/28/2011] [Indexed: 11/03/2022] Open
Abstract
INTRODUCTION The aim of the present study was to validate prothrombin time (PT) international normalized ratio (INR) results obtained using Steelex test reagents and a Steelex coagulometer (Steelex Scientific Instrument Company, Beijing, China), in comparison with use of a well-established standard test employing Pacific Hemostasis reagents (Fisher Diagnostics, Middletown, VA, USA) and Teco Coatron A4 coagulometer (Teco Medical Instruments GmbH, Neufahrn, Germany). MATERIALS AND METHODS Between- and within-day coefficients of variation (CVs) of both assays were calculated using control samples provided by the test manufacturers. Samples from 90 subjects were collected and INR values were determined in a double-blind parallel manner employing both systems. RESULTS The within-day coefficients of variation (CVs) in INR estimates ranged from 2.6% (INR = 1.12) to 3.1% (INR = 2.51) for the Steelex system and from 2.1% (INR = 1.09) to 1.8% (INR = 2.8) for the Pacific test; the between-day values ran from 3.4% (INR = 1.16) to 7.9% (INR = 2.64) and from 3.3% (INR = 1.1) to 2.3% (INR = 2.7), respectively. Passing-Bablok fit of the of the Steelex and Pacific methods yielded the equation: Steelex INR = 0.85 (0.79-0.91) x Pacific INR + 0.12 (-0.02-0.21), whereas the CUSUM linearity P value was < 0.01. The mean bias as determined by the Bland-Altman test was -0.156 (-0.912-0.600). CONCLUSION The results obtained using Steelex reagents and the M600H coagulometer are not equivalent to those obtained using Pacific Hemostasis reagents and a Teco Coatron A4 coagulometer, at least in the therapeutic range.
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Affiliation(s)
- Yasemin U Budak
- Department of Clinical Laboratory, Sevket Yilmaz Education and Training Hospital, Bursa, Turkey.
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Prothrombin time standardisation in canine samples with regard to inter-batch and inter-reagent variability. Vet J 2011; 188:301-6. [DOI: 10.1016/j.tvjl.2010.06.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Revised: 06/08/2010] [Accepted: 06/08/2010] [Indexed: 11/24/2022]
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Poller L, Ibrahim S, Keown M, Pattison A, Jespersen J. The prothrombin time/international normalized ratio (PT/INR) Line: derivation of local INR with commercial thromboplastins and coagulometers--two independent studies. J Thromb Haemost 2011; 9:140-8. [PMID: 20942851 DOI: 10.1111/j.1538-7836.2010.04109.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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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Affiliation(s)
- L Poller
- EAA Central Facility, Faculty of Life Sciences, University of Manchester, Manchester, UK.
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Poller L, Ibrahim S, Keown M, Pattison A, Jespersen J. Simplified Method for International Normalized Ratio (INR) Derivation Based on the Prothrombin Time/INR Line: An International Study. Clin Chem 2010; 56:1608-17. [DOI: 10.1373/clinchem.2009.141937] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
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, have proved to be obstacles to application 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, 2.04 with bovine/combined, and 2.80 with rabbit. 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 increased to 92.1% with local ISI calibration and 93.2% 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.
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Affiliation(s)
- Leon Poller
- European Action on Anticoagulation (EAA) Central Facility, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK
| | - Saied Ibrahim
- European Action on Anticoagulation (EAA) Central Facility, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK
| | - Michelle Keown
- European Action on Anticoagulation (EAA) Central Facility, Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK
| | | | - Jørgen Jespersen
- Department of Clinical Biochemistry, Hospital of South West Denmark, Esbjerg, and Department for Thrombosis Research, Institute of Public Health, University of Southern Denmark, Esbjerg, Denmark
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Poller L, Keown M, Ibrahim S, van den Besselaar AMHP, Roberts C, Stevenson K, Tripodi A, Pattison A, Jespersen J. Comparison of local International Sensitivity Index calibration and 'Direct INR' methods in correction of locally reported International Normalized Ratios: an international study. J Thromb Haemost 2007; 5:1002-9. [PMID: 17367490 DOI: 10.1111/j.1538-7836.2007.02452.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND It is no longer feasible to check local International Normalized Ratios (INR) by the World Health Organization International Sensitivity Index (ISI) calibrations because the necessary manual prothrombin time technique required has generally been discarded. OBJECTIVES An international collaborative study at 77 centers has compared local INR correction using the two alternative methods recommended in the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis guidelines: local ISI calibration and 'Direct INR'. METHODS Success of INR correction by local ISI calibration and with Direct INR was assessed with a set of 27 certified lyophilized plasmas (20 from patients on warfarin and seven from normals). RESULTS At 49 centers using human thromboplastins, 3.0% initial average local INR deviation from certified INR was reduced by local ISI calibration to 0.7%, and at 25 centers using rabbit reagents, from 15.9% to 7.5%. With a minority of commercial thromboplastins, mainly 'combined' rabbit reagents, INR correction was not achieved by local ISI calibration. However, when rabbit combined reagents were excluded the overall mean INR deviation after correction was reduced further to 3.9%. In contrast, with Direct INR, mean deviation using human thromboplastins increased from 3.0% to 6.6%, but there was some reduction with rabbit reagents from 15.9% to 10% (12.3% with combined reagents excluded). CONCLUSIONS Local ISI calibration gave INR correction for the majority of PT systems but failed at the small number using combined rabbit reagents suggesting a need for a combined reference thromboplastin. Direct INR correction was disappointing but better than local ISI calibration with combined rabbit reagents. Interlaboratory variability was improved by both procedures with human reagents only.
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Affiliation(s)
- L Poller
- The European Concerted Action on Anticoagulation Central Facility, University of Manchester, Faculty of Life Sciences, Manchester, UK.
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van den Besselaar AMHP, Barrowcliffe TW, Houbouyan-Réveillard LL, Jespersen J, Johnston M, Poller L, Tripodi A. Guidelines on preparation, certification, and use of certified plasmas for ISI calibration and INR determination. J Thromb Haemost 2004; 2:1946-53. [PMID: 15550026 DOI: 10.1111/j.1538-7836.2004.00970.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reliable international normalized ratio (INR) determination depends on accurate values for international sensitivity index (ISI) and mean normal prothrombin time (MNPT). Local ISI calibration can be performed to obtain reliable INR. Alternatively, the laboratory may determine INR directly from a line relating local log(prothrombin time [PT]) to log(INR). This can be done by means of lyophilized or frozen plasmas to which certified values of PT or INR have been assigned. Currently there is one procedure for local calibration with certified plasmas which is a modification of the WHO method of ISI determination. In the other procedure, named 'direct' INR determination, certified plasmas are used to calculate a line relating log(PT) to log(INR). The number of certified plasmas for each procedure depends on the method of preparation and type of plasma. Lyophilization of plasma may induce variable effects on the INR, the magnitude of which depends on the type of thromboplastin used. Consequently, the manufacturer or supplier of certified plasmas must assign the values for different (reference) thromboplastins and validate the procedure for reliable ISI calibration or 'direct' INR determination. Certification of plasmas should be performed by at least three laboratories. Multiple values should be assigned if the differences between thromboplastin systems are greater than 10%. Testing of certified plasmas for ISI calibration may be performed in quadruplicate in the same working session. It is recommended to repeat the measurements on three sessions or days to control day-to-day variation. Testing of certified plasmas for 'direct' INR determination should be performed in at least three sessions or days. Correlation lines for ISI calibration and for 'direct' INR determination should be calculated by means of orthogonal regression. Quality assessment of the INR with certified plasmas should be performed regularly and should be repeated whenever there is a change in reagent batch or in instrument. Discrepant results obtained by users of certified plasmas should be reported to manufacturers or suppliers.
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Affiliation(s)
- A M H P van den Besselaar
- Hemostasis and Thrombosis Research Center, Department of Hematology, Leiden University Medical Center, The Netherlands.
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Affiliation(s)
- L Poller
- The University of Manchester, Manchester, UK.
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van den Besselaar AMHP, Houdijk WPM. Use of Lyophilized Calibrant Plasmas for Simplified International Normalized Ratio Determination with a Human Tissue Factor Thromboplastin Reagent Derived from Cultured Human Cells. Clin Chem 2003; 49:2006-11. [PMID: 14633871 DOI: 10.1373/clinchem.2003.023531] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Abstract
Background: For monitoring of treatment with oral anticoagulants, the clotting time obtained in the prothrombin time (PT) test is transformed to the International Normalized Ratio (INR) with use of a system-specific International Sensitivity Index (ISI). The calibrant plasma procedure (CPP) is an alternative approach to INR calculation based on the use of a set of lyophilized plasmas with assigned INRs.
Methods: With the CPP, a linear relationship is established between log(PT) and log(INR), using orthogonal regression. CPP was validated for Simplastin HTF, a new human tissue factor reagent derived from cultured human cells. CPP precision was assessed as the CV of the slope of the regression line. The accuracy of the CPP was determined by comparing the INR obtained with the CPP with that obtained with the established ISI-based reference method. INRs of the calibrants were assigned by different routes: by manufacturer (consensus labeling) or by use of Simplastin HTF or International Reference Preparations (IRPs; rTF/95 or RBT/90).
Results: The mean CV of the CPP regression slope ranged from 1.0% (Simplastin HTF reagent-specific INR) to 2.4% (INR assigned with rTF/95). INRs calculated with the CPP were similar to those obtained with the reference method, but when the routes for assigning INRs to the calibrant plasmas were compared, the mean difference in INR between CPP and the reference method was smaller with Simplastin HTF reagent-specific values. In several (but not all) cases, this difference was significant (P <0.05, t-test).
Conclusion: CPP can be used for local INR determination, but better precision and accuracy are obtained with reagent-specific INRs compared with INR assignment by consensus labeling or IRP.
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Affiliation(s)
- Anton M H P van den Besselaar
- Haemostasis and Thrombosis Research Center, Department of Haematology, Leiden University Medical Center, Leiden, The Netherlands
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Hirsh J, Fuster V, Ansell J, Halperin JL. American Heart Association/American College of Cardiology Foundation guide to warfarin therapy. J Am Coll Cardiol 2003; 41:1633-52. [PMID: 12742309 DOI: 10.1016/s0735-1097(03)00416-9] [Citation(s) in RCA: 226] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Hirsh J, Fuster V, Ansell J, Halperin JL. American Heart Association/American College of Cardiology Foundation guide to warfarin therapy. Circulation 2003; 107:1692-711. [PMID: 12668507 DOI: 10.1161/01.cir.0000063575.17904.4e] [Citation(s) in RCA: 409] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Hirsh J, Dalen J, Anderson DR, Poller L, Bussey H, Ansell J, Deykin D. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest 2001; 119:8S-21S. [PMID: 11157640 DOI: 10.1378/chest.119.1_suppl.8s] [Citation(s) in RCA: 649] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Affiliation(s)
- J Hirsh
- Hamilton Civics Hospitals Research Centre, Ontario, Canada
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Dufour DR, Lott JA, Nolte FS, Gretch DR, Koff RS, Seeff LB. Diagnosis and Monitoring of Hepatic Injury. I. Performance Characteristics of Laboratory Tests. Clin Chem 2000. [DOI: 10.1093/clinchem/46.12.2027] [Citation(s) in RCA: 333] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
AbstractPurpose: To review information on performance characteristics for tests that are commonly used to identify acute and chronic hepatic injury.Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic tests, including quality specifications, aminotransferases, alkaline phosphatase, γ-glutamyltransferase, bilirubin, albumin, ammonia, and viral markers. Abstracts were reviewed, and articles discussing performance of laboratory tests were selected for review. Additional articles were selected from the references.Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact. The drafts were also reviewed by the Practice Guidelines Committee of the American Association for the Study of Liver Diseases and approved by the committee and the Association’s Council.Recommendations: Although many specific recommendations are made in the guidelines, some summary recommendations are discussed here. Alanine aminotransferase is the most important test for recognition of acute and chronic hepatic injury. Performance goals should aim for total error of <10% at the upper reference limit to meet clinical needs in monitoring patients with chronic hepatic injury. Laboratories should have age-adjusted reference limits for enzymes in children, and gender-adjusted reference limits for aminotransferases, γ-glutamyltransferase, and total bilirubin in adults. The international normalized ratio should not be the sole method for reporting results of prothrombin time in liver disease; additional research is needed to determine the reporting mechanism that best correlates with functional impairment. Harmonization is needed for alanine aminotransferase activity, and improved standardization for hepatitis C viral RNA measurements.
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Affiliation(s)
- D Robert Dufour
- Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center, Washington, DC 20422, and Department of Pathology, George Washington University School of Medicine, Washington, DC 20037
| | - John A Lott
- Department of Pathology, The Ohio State University College of Medicine, Columbus, OH 43210
| | - Frederick S Nolte
- Departments of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322
| | - David R Gretch
- Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98104-2499
| | - Raymond S Koff
- Department of Medicine, University of Massachusetts Medical Center, Worchester, MA 06155
| | - Leonard B Seeff
- Hepatitis C Programs, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, and Georgetown University School of Medicine, Washington, DC 20037
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21
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Poller L, Keown M, Shepherd SA, Shiach CR, Tabeart S. The effects of freeze drying and freeze drying additives on the prothrombin time and the international sensitivity index. J Clin Pathol 1999; 52:744-8. [PMID: 10674031 PMCID: PMC501567 DOI: 10.1136/jcp.52.10.744] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIM To determine whether freezing, freeze drying protective additives, or freeze drying of plasma samples from patients on coumarin treatment and from normal individuals affects prothrombin times or the international sensitivity index (ISI) calibration. METHODS The effect of the addition of the protective additives singly and combined on the prothrombin time of coumarin samples and normal samples before and after freeze drying was observed using high and low ISI reference thromboplastins. ISI values were also determined. RESULTS Freezing caused a prolongation of prothrombin time in the normal plasma samples with both reagents, which was significant with the low ISI human. Prolongation (non-significant) of the prothrombin time in coumarin plasma samples occurred with the human reagent only. Significant prolongation of normal prothrombin time by some of the protective additives before and after freeze drying was observed with both thromboplastins but to a greater extent with the human. Significant prolongation of prothrombin time in coumarin plasma samples was observed, but again was more marked with human thromboplastin. An approximate ISI was determined on the 20 coumarin samples. The only marked ISI change was with the WHO human thromboplastin after freeze drying of plasma, where a decrease from 0.95 to 0.90 was observed, corresponding to a marked prothrombin ratio increase. CONCLUSIONS Freeze drying additives and the freeze drying procedure prolong normal and coumarin prothrombin times, with low ISI thromboplastin. Less marked prolongations occurred with a high ISI rabbit reagent, coumarin samples showing more significant prolongations. Marked ISI change in freeze dried plasma was only recorded with the low ISI ECAA human reagent. Frozen normal plasma samples cannot be used with confidence for ISI calibrations.
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Affiliation(s)
- L Poller
- European Concerted Action on Anticoagulation, School of Biological Sciences, University of Manchester, UK.
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22
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Hubbard AR, Margetts SM, Weller LJ, Macnab J, Barrowcliffe TW. An international collaborative study on the INR calibration of freeze-dried reference plasmas. Br J Haematol 1999; 104:455-60. [PMID: 10086778 DOI: 10.1046/j.1365-2141.1999.01225.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A study was carried out to calibrate potential European Reference Plasmas for prothrombin time (PT) standardization. The International Normalized Ratio (INR) values of three freeze-dried candidate plasmas (one pooled normal and two pools from anticoagulated patients) were determined in 20 laboratories using six thromboplastin reagents comprising three International Reference Thromboplastins (human, rabbit and bovine), two recombinant human reagents and one placental human reagent. Interlaboratory variability of INR estimation was low with geometric coefficients of variation (gcv) <10% except in one case. Significant differences in mean INR were found between the different thromboplastins with lowest INR values found with the bovine reagent. INR values from the International rabbit and human reagents differed by <6% and were combined to give proposed assigned INR values. Significant differences in INR estimates from four thromboplastins of human origin may indicate that single assigned INR values are not applicable for use with all thromboplastin reagents. Field trials to assess the validity of single assigned INR values in clinical practice are required.
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Affiliation(s)
- A R Hubbard
- Division of Haematology, National Institute for Biological Standards and Control, Potters Bar, Herts
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23
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Hirsh J, Dalen JE, Anderson DR, Poller L, Bussey H, Ansell J, Deykin D, Brandt JT. Oral anticoagulants: mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest 1998; 114:445S-469S. [PMID: 9822057 DOI: 10.1378/chest.114.5_supplement.445s] [Citation(s) in RCA: 336] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Affiliation(s)
- J Hirsh
- Research Centre, Hamilton Civic Hospitals, ON, Canada
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24
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Poller L, van den Besselaar AM, Jespersen J, Tripodi A, Houghton D. A comparison of linear and orthogonal regression analysis for local INR determination in ECAA coagulometer studies. European Concerted Action on Anticoagulation. Br J Haematol 1998; 102:910-7. [PMID: 9734639 DOI: 10.1046/j.1365-2141.1998.00866.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
International sensitivity index calibrations based on the W.H.O. recommended method depend on orthogonal regression analysis. As this is not readily available in statistical packages, comparison has been made with simple linear regression analysis in a study of coagulometer effects on the International Normalized Ratio (INR) at 155 European centres. Sets of seven lyophilized normal and 20 lyophilized artificially depleted abnormal plasmas were provided with five coumarin test plasmas and two European Concerted Action on Anticoagulation reference thromboplastins (low International Sensitivity Index (ISI) human and high ISI rabbit). Local ISI based on the artificially depleted lyophilized plasmas using conventional orthogonal regression gave good correction for local coagulometer effects on the human reagent and minimal correction with the rabbit reagent INR. Results were considerably worse after attempts at correction using calibration based on linear regression analysis with both reagents. The results indicate that calibration of coagulometer prothrombin time systems using simple linear regression is not appropriate.
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Affiliation(s)
- L Poller
- Central Facility, ECAA, University of Manchester, UK
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25
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Poller L, van den Besselaar AM, Jespersen J, Tripodi A, Houghton D. A comparison of artificially-depleted, lyophilized coumarin and fresh coumarin plasmas in thromboplastin calibration. European Concerted Action on Anticoagulation. Br J Haematol 1998; 101:462-7. [PMID: 9633887 DOI: 10.1046/j.1365-2141.1998.00728.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Artificially-depleted lyophilized plasmas and lyophilized coumarin plasmas were prepared and compared with fresh coumarin plasmas to assess their comparative reliability in local thromboplastin calibration using the manual prothrombin time (PT) technique. Their certified PT values were inserted in turn on the vertical axis in place of the PT obtained with fresh coumarin plasmas. PT results were obtained at eight ECAA national laboratories ('test centres') and inserted on the horizontal axis. The resulting thromboplastin calibration slopes were compared with conventional fresh coumarin plasma calibration slopes at the same 'test centres'. When 60 artificially-depleted plasmas were substituted for 60 fresh plasmas, the mean calibration slopes with the human plain International Reference Preparation (IRP) were 4.2% higher. For comparison with 20 lyophilized coumarins, three sets of 20 artificially-depleted plasmas were selected in sequential order from the 60. The lyophilized coumarin plasmas gave a mean deviation of 9.6% from the fresh plasma calibration slopes compared with values of 2.0%, 6.1% and 11.7% for the three sets of 20 depleted plasmas. Although both types of lyophilized plasma calibration slopes give measurable differences from conventional fresh plasmas, these may be regarded as acceptable in clinical terms.
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Affiliation(s)
- L Poller
- Central Facility, ECAA, Department of Pathological Sciences, University of Manchester, UK
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26
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Abstract
AIM To assess the reliability of local international normalised ratios (INR) using a set of three international reference preparation (IRP) certified freeze dried plasmas. METHODS 55 centres in the United Kingdom and the Republic of Ireland participated; 36 centres employed coagulometers and 19 a manual prothrombin time technique, all with the same batch of routine commercial thromboplastin. The plasmas had certified INR with the manual technique using a thromboplastin IRP, and results were provided graphically to participants for self assessment. An INR deviation of more than +/- 10% from the certified INR with any of the screening plasmas was regarded as unsatisfactory and clinically significant. Sets of 20 freeze dried plasmas were provided for local ISI calibrations and sets of seven freeze dried normals were provided for supplementary exercises where screening results were unsatisfactory. RESULTS 15 of 38 coagulometers, but only three of the 19 manual prothrombin time test techniques, gave unsatisfactory results. With 10 of the 15 unsatisfactory coagulometer results the problem was resolved by local ISI calibrations with plasma calibrant sets provided. Unsatisfactory results with manual technique in all four instances were corrected by substitution of the mean result with freeze dried normal plasmas provided. CONCLUSIONS The freeze dried plasma screening set was useful in detecting incorrect INR in a high proportion of coagulometer users and a smaller number of participants using the manual technique.
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Affiliation(s)
- L Poller
- Department of Pathological Sciences, University of Manchester, UK
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Cachia PG, McGregor E, Adlakha S, Davey P, Goudie BM. Accuracy and precision of the TAS analyser for near-patient INR testing by non-pathology staff in the community. J Clin Pathol 1998; 51:68-72. [PMID: 9577376 PMCID: PMC500435 DOI: 10.1136/jcp.51.1.68] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIMS To assess the accuracy and precision of INR measurement by trained practice and district nursing staff using the Thrombolytic Assessment System (TAS) analyser. METHODS Seventeen nurses from four practices were trained to measure INR using the TAS analyser on citrated capillary blood samples. Quality control (QC) consisted of: daily internal QC using normal and abnormal commercial plasmas; monthly local external QC scheme using fresh citrated venous blood; and registration of all analysers in the NEQAS (national external quality assessment scheme) main users scheme. RESULTS Analysis of internal QC results demonstrated satisfactory interanalyser and intra-analyser precision with no evidence of analytical drift in any of the four practice analysers over an eight month period. Local and national external QC results confirmed the interanalyser precision but INR was underestimated by the TAS analysers compared with the CA 1000 using either Diagen rabbit brain thromboplastin or Innovin, and with other NEQAS users. CONCLUSIONS The TAS analyser has many features to commend it for use by nonpathology staff to determine INR. Local internal and external QC and entry into the NEQAS main users group are possible because the TAS analyses citrated plasma or blood. The TAS analyser underestimates INR when the geometric mean normal prothrombin time (GMNPT) is determined by conventional methods. A local correction factor can be introduced by adjusting the normal PT to give INR results comparable with the local laboratory. This is particularly desirable when INRs are measured using both near-patient and laboratory analytical systems on different occasions.
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Affiliation(s)
- P G Cachia
- Department of Haematology, Ninewells Hospital, Dundee, UK.
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29
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van den Besselaar AM. Field study of lyophilised plasmas for local prothrombin time calibration in The Netherlands. J Clin Pathol 1997; 50:371-4. [PMID: 9215117 PMCID: PMC499936 DOI: 10.1136/jcp.50.5.371] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
AIM To assess the effect of a lyophilised calibrant plasma procedure on the international normalised ratio (INR) and its interlaboratory variation. METHODS INR equivalent values were assigned to five lyophilised plasmas (one from normal donors and four from coumarin treated patients) by a reference laboratory using three calibrated thromboplastin reagents. The calibrant plasmas and five artificial control blood specimens were mailed to 44 Dutch laboratories for prothrombin time (PT) determination. The assigned INR values were used to calculate calibration lines for each participant laboratory. The calibration lines were then used to translate the PT of the control specimens to INR. RESULTS For all lyophilised plasmas and control blood samples, there were significant differences between INR values determined with the three thromboplastin reagents. These differences could not be explained by inaccuracy of the international sensitivity index or mean normal PT of the reagents and must, therefore, have been induced by the preparation procedures for the lyophilised plasmas and control blood samples. The interlaboratory variation of the INR obtained with the calibrant plasma procedure had a coefficient of variation (CV) ranging between 2.1% and 7.3% and tended to be lower than the interlaboratory variation found with the usual methods (3.0-12.2% CV). There was a good agreement between the mean INRs obtained with the calibrant procedure and those obtained using the normal methods. CONCLUSIONS The present study highlights the limitations of some lyophilised plasmas and control blood samples. It is not possible to assign a single INR value to each of these lyophilised plasmas and control specimens that is valid for all thromboplastin reagents. Nevertheless, by using reagent specific INR equivalent values for the calibrant plasma procedure, the interlaboratory variation could be reduced.
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30
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Hirsh J, Dalen JE, Deykin D, Poller L, Bussey H. Oral anticoagulants. Mechanism of action, clinical effectiveness, and optimal therapeutic range. Chest 1995; 108:231S-246S. [PMID: 7555179 DOI: 10.1378/chest.108.4_supplement.231s] [Citation(s) in RCA: 193] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
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