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Laboratory international normalized ratios determined with commercial thromboplastins in >450 centers before and after the establishment of the International Standard for human thromboplastin-rTF 16: data from United Kingdom National External Quality Assessment Scheme for Blood Coagulation. J Thromb Haemost 2023; 21:1385-1387. [PMID: 36758727 DOI: 10.1016/j.jtha.2023.01.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 02/10/2023]
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Tripodi A, Scalambrino E, Clerici M, Chantarangkul V, Peyvandi F. Thromboplastin calibration revisited to look for possible revision of the World Health Organization recommendations. JOURNAL OF THROMBOSIS AND HAEMOSTASIS : JTH 2023; 21:311-316. [PMID: 36700497 DOI: 10.1016/j.jtha.2022.11.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 11/08/2022] [Accepted: 11/12/2022] [Indexed: 01/26/2023]
Abstract
BACKGROUND Thromboplastin calibration is essential to determine the international sensitivity index required to calculate the international normalized ratio (INR). The procedure for calibration recommended by the World Health Organization (WHO) calls for the selection of patients on stable anticoagulation in the range of 1.5 to 4.5 INR. These patients are difficult to be recruited as the conventional therapeutic interval for warfarin is 2.0 to 3.0. A possible solution could be including patients with less intense anticoagulation in the calibration. OBJECTIVES We sought to investigate the impact of this amended procedure on the parameters of calibration. METHODS Eight data sets from previous calibrations of a rabbit thromboplastin that included patients on anticoagulation as required by WHO were used for this pilot study. Parameters of calibration as determined by the full data sets are identified as "full calibrations" and are considered reference. Each of the data sets were used to recalculate the calibration parameters after including patients with INRs of <4.0, <3.5, or <3.0, which were identified as "trimmed calibrations" and compared with those from the full calibrations. RESULTS There was marginal variation of the international sensitivity index, CV, and INR that can be hardly of practical significance. CV was the most affected parameter, which increased from the full to the trimmed <3.0 calibration, but never exceeded the 3% cutoff value recommended by WHO. CONCLUSIONS Should the results of this pilot study be confirmed for the calibration of other thromboplastins, revision of the WHO recommendations to include patients with INR from 1.5 to 4.0 is warranted.
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Affiliation(s)
- Armando Tripodi
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano and Fondazione Luigi Villa, Milano, Italy.
| | - Erica Scalambrino
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano and Fondazione Luigi Villa, Milano, Italy
| | - Marigrazia Clerici
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano and Fondazione Luigi Villa, Milano, Italy
| | - Veena Chantarangkul
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano and Fondazione Luigi Villa, Milano, Italy
| | - Flora Peyvandi
- Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Milano and Fondazione Luigi Villa, Milano, Italy; Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Milano, Italy
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Humphries TLR, Johnson LA, Masci PP, Gobe GC, Vesey DA. Progress curve analysis of microtitre plate plasma clotting assays. Assessment of tissue factor levels. Anal Biochem 2020; 614:114060. [PMID: 33271154 DOI: 10.1016/j.ab.2020.114060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/23/2020] [Accepted: 11/27/2020] [Indexed: 11/25/2022]
Abstract
MTP plasma clotting assays monitor the time course of fibrin formation in re-calcified plasma by absorbance measurements and are increasingly used as alternatives to traditional one-point clot time assays employed in clinical laboratories to detect thrombotic disorders. The parameters derived from these analyses are analogous to thromboelastography viz. time, rate and maximum extent of clot formation. The derived parameters, based on the whole course of the clotting reaction are more robust, informative and quantitative than single-point clot time assays. However, the parameters themselves are usually obtained arbitrarily by crude graphical analysis of subjectively selected points of progress curves. The current work aimed to investigate the sensitivity and reproducibility of an MTP clotting assay and examine its suitability for measuring tissue factor (TF) levels in cell culture medium and patient urine. The results demonstrate that progress curves can be analysed by fitting a logistic equation, derived from a simplified autocatalytic clot formation model. The parameters, maximum amplitude (Fm), rate constant (k), time to half-maximum amplitude (tm) and maximum rate of clot formation (vm), fit a power curve showing limiting effects with increasing TF concentration. Log/log plots of tm and k against TF concentration provide standard curves for assessment of unknowns.
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Affiliation(s)
- Tyrone L R Humphries
- Kidney Disease Research Collaborative, Princess Alexandra Hospital, University of Queensland and Translational Research Institute, Brisbane, Australia
| | - Lambro A Johnson
- Centre for Venomics Research, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia
| | - Paul P Masci
- Centre for Venomics Research, School of Medicine, University of Queensland, Translational Research Institute, Brisbane, Australia
| | - Glenda C Gobe
- Kidney Disease Research Collaborative, Princess Alexandra Hospital, University of Queensland and Translational Research Institute, Brisbane, Australia
| | - David A Vesey
- Kidney Disease Research Collaborative, Princess Alexandra Hospital, University of Queensland and Translational Research Institute, Brisbane, Australia.
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van den Besselaar AMHP, Cobbaert CM. Assignment of international normalized ratio to frozen and freeze-dried pooled plasmas. Clin Chem Lab Med 2020; 58:2089-2097. [PMID: 32840098 DOI: 10.1515/cclm-2019-1321] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/29/2020] [Indexed: 11/15/2022]
Abstract
Objectives Frozen and freeze-dried plasmas may be used for local prothrombin time system calibration, for direct international normalized ratio (INR) determination, and for quality assessment. The purpose of the present study was to evaluate the usefulness of INRs assigned with various types of thromboplastins to frozen and freeze-dried pooled plasmas obtained from patients treated with vitamin K antagonists. Methods INRs were calculated according to the international sensitivity index (ISI) model using various thromboplastins and instruments, i.e. International Standards for thromboplastin as well as six commercial reagents prepared from rabbit and bovine brain, and recombinant human tissue factor. The uncertainty of the INRs was assessed using the standard deviations of clotting times and ISI values. Commutability of the plasmas was assessed according to the approved Clinical and Laboratory Standards Institute (CLSI) Guideline EP30-A. Validation of a set of six frozen plasma pools for direct INR determination was performed according to the Subcommittee on Control of Anticoagulation of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis (SSC/ISTH) guidelines. Results For all frozen and freeze-dried plasmas, the INRs calculated with bovine thromboplastin Thrombotest were lower than the INRs assigned with other thromboplastins. With a few exceptions, the frozen and freeze-dried pooled plasmas were commutable. When the set of six frozen plasma pools was used for local calibration, the analytical bias of the INR was less than ±10% for all commercial reagents except Thrombotest. Conclusions Processing of fresh plasmas to prepare pooled frozen plasmas and freeze-dried plasmas may lead to different INR assignments depending on the thromboplastin used. Despite minor INR differences, a set of six frozen plasma pools could be used for local calibration by direct INR determination.
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Affiliation(s)
- Antonius M H P van den Besselaar
- Coagulation Reference Laboratory, Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.,Department of Thrombosis and Hemostasis, Leiden University Medical Center, Leiden, The Netherlands, Phone: +31 71 526 1942
| | - Christa M Cobbaert
- Coagulation Reference Laboratory, Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, The Netherlands
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van den Besselaar AMHP, Chantarangkul V, Angeloni F, Binder NB, Byrne M, Dauer R, Gudmundsdottir BR, Jespersen J, Kitchen S, Legnani C, Lindahl TL, Manning RA, Martinuzzo M, Panes O, Pengo V, Riddell A, Subramanian S, Szederjesi A, Tantanate C, Herbel P, Tripodi A. International collaborative study for the calibration of proposed International Standards for thromboplastin, rabbit, plain, and for thromboplastin, recombinant, human, plain. J Thromb Haemost 2018; 16:142-149. [PMID: 29065247 DOI: 10.1111/jth.13879] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Indexed: 11/28/2022]
Abstract
Essentials Two candidate International Standards for thromboplastin (coded RBT/16 and rTF/16) are proposed. International Sensitivity Index (ISI) of proposed standards was assessed in a 20-centre study. The mean ISI for RBT/16 was 1.21 with a between-centre coefficient of variation of 4.6%. The mean ISI for rTF/16 was 1.11 with a between-centre coefficient of variation of 5.7%. SUMMARY Background The availability of International Standards for thromboplastin is essential for the calibration of routine reagents and hence the calculation of the International Normalized Ratio (INR). Stocks of the current Fourth International Standards are running low. Candidate replacement materials have been prepared. This article describes the calibration of the proposed Fifth International Standards for thromboplastin, rabbit, plain (coded RBT/16) and for thromboplastin, recombinant, human, plain (coded rTF/16). Methods An international collaborative study was carried out for the assignment of International Sensitivity Indexes (ISIs) to the candidate materials, according to the World Health Organization (WHO) guidelines for thromboplastins and plasma used to control oral anticoagulant therapy with vitamin K antagonists. Results Results were obtained from 20 laboratories. In several cases, deviations from the ISI calibration model were observed, but the average INR deviation attributabled to the model was not greater than 10%. Only valid ISI assessments were used to calculate the mean ISI for each candidate. The mean ISI for RBT/16 was 1.21 (between-laboratory coefficient of variation [CV]: 4.6%), and the mean ISI for rTF/16 was 1.11 (between-laboratory CV: 5.7%). Conclusions The between-laboratory variation of the ISI for candidate material RBT/16 was similar to that of the Fourth International Standard (RBT/05), and the between-laboratory variation of the ISI for candidate material rTF/16 was slightly higher than that of the Fourth International Standard (rTF/09). The candidate materials have been accepted by WHO as the Fifth International Standards for thromboplastin, rabbit plain, and thromboplastin, recombinant, human, plain.
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Affiliation(s)
- A M H P van den Besselaar
- Department of Thrombosis and Hemostasis, and Coagulation Reference Laboratory, Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, the Netherlands
| | | | - F Angeloni
- Hemostasis Reference Laboratory, Hamilton, Canada
| | | | - M Byrne
- National Coagulation Laboratory, St James's Hospital, Dublin, Ireland
| | - R Dauer
- Haematology Laboratory, Pathology Department, Alfred Health, Melbourne, Australia
| | - B R Gudmundsdottir
- Department of Laboratory Hematology and Hemostasis Center, Landspitali University Hospital and University of Iceland School of Medicine, Reykjavik, Iceland
| | - J Jespersen
- Department of Clinical Biochemistry, Hospital of South West Jutland and Unit for Health Promotion Research, Institute of Public Health, University of Southern Denmark, Esbjerg, Denmark
| | - S Kitchen
- Sheffield Haemophilia and Thrombosis Centre, Royal Hallamshire Hospital, Sheffield, UK
| | - C Legnani
- Department of Angiology and Blood Coagulation, University Hospital S. Orsola-Malpighi, Bologna, Italy
| | - T L Lindahl
- Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
| | - R A Manning
- Department of Coagulation, Hammersmith Hospital, Imperial College Healthcare NHS Trust, London, UK
| | - M Martinuzzo
- Grupo Bioquímico, Laboratorio Central del Hospital Italiano de Buenos Aires, Buenos Aires, Argentina
| | - O Panes
- Department of Hematology-Oncology, School of Medicine, Pontifical Catholic University of Chile, Santiago, Chile
| | - V Pengo
- Clinical Cardiology, Department of Cardiac, Thoracic, and Vascular Sciences, University of Padova, Padova, Italy
| | - A Riddell
- Haemophilia Laboratory (HSL), Katharine Dormandy Haemophilia and Thrombosis Centre, Royal Free Hospital, London, UK
| | - S Subramanian
- Department of Transfusion Medicine and Immunohaematology, St John's Medical College Hospital, Bangalore, India
| | - A Szederjesi
- Hemostasis Laboratory, St István and St László Hospital, Budapest, Hungary
| | - C Tantanate
- Department of Clinical Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - P Herbel
- Roche Diagnostics GmbH Mannheim, Mannheim, Germany
| | - A Tripodi
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Clinical Sciences and Community Health, Università degli Studi di Milano and IRCCS Cà Granda Maggiore Hospital Foundation, Milano, Italy
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Biedermann JS, van den Besselaar AMHP, de Maat MPM, Leebeek FWG, Kruip MJHA. Monitoring of treatment with vitamin K antagonists: recombinant thromboplastins are more sensitive to factor VII than tissue-extract thromboplastins. J Thromb Haemost 2017; 15:500-506. [PMID: 28055147 DOI: 10.1111/jth.13611] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Indexed: 11/29/2022]
Abstract
Essentials Differences in sensitivity to factor VII (FVII) have been suggested between thromboplastins. FVII-induced International Normalized Ratio (INR) changes differ between commercial reagents. Recombinant human thromboplastins are more sensitive to FVII than tissue-extract thromboplastins. Thromboplastin choice may affect FVII-mediated INR stability. SUMMARY Background Differences regarding sensitivity to factor VII have been suggested for recombinant human and tissue-extract thromboplastins used for International Normalized Ratio (INR) measurement, but the evidence is scarce. Differences in FVII sensitivity are clinically relevant, as they can affect INR stability during treatment with vitamin K antagonists (VKAs). Objectives To determine whether commercial thromboplastins react differently to changes in FVII. Methods We studied the effect of addition of FVII on the INR in plasma by using three tissue-extract (Neoplastin C1+, Hepato Quick, and Thromborel S) and three recombinant human (Recombiplastin 2G, Innovin, and CoaguChek XS) thromboplastins. Three different concentrations of purified human FVII (0.006, 0.012 and 0.062 μg mL-1 plasma), or buffer, were added to five certified pooled plasmas of patients using VKAs (INR of 1.5-3.5). Changes in FVII activity were measured with two bioassays (Neoplastin and Recombiplastin), and relative INR changes were compared between reagents. Results After addition of 0.062 μg mL-1 FVII, FVII activity in the pooled plasmas increased by approximately 20% (Neoplastin) or 32% (Recombiplastin) relative to the activity in pooled normal plasma. All thromboplastins showed dose-dependent INR decreases. The relative INR change in the pooled plasmas significantly differed between the six thromboplastins. No differences were observed among recombinant or tissue-extract thromboplastins. Pooled results indicated that the FVII-induced INR change was greater for recombinant than for tissue-extract thromboplastins. Conclusions Differences regarding FVII sensitivity exist between various thromboplastins used for VKA monitoring. Recombinant human thromboplastins are more sensitive to FVII than tissue-extract thromboplastins. Therefore, thromboplastin choice may affect FVII-mediated INR stability.
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Affiliation(s)
- J S Biedermann
- Department of Hematology, Erasmus University Medical Center, Rotterdam, the Netherlands
- Star-Medical Diagnostic Center, Rotterdam, the Netherlands
| | | | - M P M de Maat
- Department of Hematology, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - F W G Leebeek
- Department of Hematology, Erasmus University Medical Center, Rotterdam, the Netherlands
| | - M J H A Kruip
- Department of Hematology, Erasmus University Medical Center, Rotterdam, the Netherlands
- Star-Medical Diagnostic Center, Rotterdam, the Netherlands
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Tripodi A, Lippi G, Plebani M. How to report results of prothrombin and activated partial thromboplastin times. ACTA ACUST UNITED AC 2016; 54:215-22. [DOI: 10.1515/cclm-2015-0657] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 07/15/2015] [Indexed: 11/15/2022]
Abstract
AbstractProthrombin time (PT) and activated partial thromboplastin time (APTT) are the most widely used tests to investigate coagulation abnormalities. Varied result reporting have been introduced over the years for the two tests, thus making their interpretation rather confusing in different clinical settings. PT results have been reported as clotting time, percentage activity, PT-ratio (patient-to-normal clotting time) and as international normalized ratio (INR). The INR scale has been devised to harmonize results stemming from different thromboplastins from patients on treatment with vitamin K antagonists. Therefore, there are some theoretical and evidence-based considerations that make the INR formally invalid when the test is used to analyze patients in other clinical settings. Unfortunately, this limitation has been frequently overlooked, and the INR has been (and is currently) used as a universal system of results harmonization. The APTT has been historically reported as clotting time or as ratio (patient-to-normal clotting time). In this opinion paper we review the current state-of-the-art for result reporting and attempt to give practical guidance on how PT and APTT should be reported in different clinical conditions for which the tests are requested.
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Long-term stability of international standards for thromboplastin stored at -20°C, -70°C, and -150°C. Thromb Res 2015; 136:164-7. [DOI: 10.1016/j.thromres.2015.04.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 04/23/2015] [Accepted: 04/26/2015] [Indexed: 11/24/2022]
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Magnusson M, Sten-Linder M, Bergquist A, Rajani R, Kechagias S, Fischler B, Németh A, Lindahl TL. The international normalized ratio according to Owren in liver disease: interlaboratory assessment and determination of international sensitivity index. Thromb Res 2013; 132:346-51. [PMID: 23993902 DOI: 10.1016/j.thromres.2013.05.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2012] [Revised: 04/28/2013] [Accepted: 05/07/2013] [Indexed: 02/06/2023]
Abstract
INTRODUCTION The international normalized ratio (INR) is used to prioritize liver disease patients for transplantation. Previous studies have shown high interlaboratory variability in Quick-based INR determinations in samples of patients with liver disease. We assessed Owren-based INR reagents for analyzing INR in patients with liver disease. Further, we determined the difference between international sensitivity index (ISI) for patients on vitamin K antagonists (ISIVKA) and ISI for patients with liver disease (ISIliver). PATIENTS AND METHODS Twenty patients with liver disease were included, 10 with INR 1.8-3.6 (group A1) and 10 with INR 1.2-1.5 (group C1). Plasma from these patients was analyzed for Owren-based INR in eight Swedish laboratories using either of following reagents: SPA+, Owrens PT or Nycotest PT. To determine ISI liver, the reference thromboplastin RBT/05 and additional 41 patients with liver disease and 20 normal controls were included. ISIVKA was determined according to the WHO procedure. The difference between the ISIVKA and ISIliver was calculated. RESULTS The coefficients of variance for the Owren based INR methods were 6.2% in group A1, 3.9 % in group C1 and 5.3% for all patients. The difference between ISIVKA and ISIliver were -0.4%, -0.7% and -0.2% for SPA+, Owrens PT and Nycotest PT respectively. CONCLUSIONS Interlaboratory variation in INR analyses according to Owren in patients with liver disease is low and the difference between ISIVKA and ISIliver is below 10% with this method. ISIVKA can therefore be used in the INR calibration, for the Owren reagents studied, when analyzing plasma from patients with liver disease.
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Affiliation(s)
- Maria Magnusson
- CLINTEC, Karolinska Institutet, Division of Pediatrics, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden.
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van den Besselaar AMHP, Witteveen E, van der Meer FJM. Uncertainty of international sensitivity index and international normalized ratio. J Thromb Haemost 2013; 11:1615-7. [PMID: 23742255 DOI: 10.1111/jth.12311] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 05/30/2013] [Indexed: 11/28/2022]
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Properties of a recombinant bovine tissue factor expressed by Silkworm pupae and its performance as an Owren-type prothrombin time reagent for warfarin monitoring. Thromb Res 2012; 130:520-7. [DOI: 10.1016/j.thromres.2012.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Revised: 05/05/2012] [Accepted: 05/11/2012] [Indexed: 11/19/2022]
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Tripodi A, Chantarangkul V, Legnani C, Fronton R, Testa S. Discrepancy of the international normalized ratio observed in the external quality assessment survey: a cause for concern. J Thromb Haemost 2012; 10:714-6. [PMID: 22934292 DOI: 10.1111/j.1538-7836.2012.04628.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- A Tripodi
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine, Università degli Studi di Milano and IRCCS Cà Granda Ospedale Maggiore Foundation, Milan; Italy
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Tripodi A, Chantarangkul V, Clerici M, Palmucci C, Bison E, Banzato A, Biguzzi E, Pengo V. Standardization of lupus anticoagulant. Feasibility study of a calibration model to minimize between-method variability. Thromb Res 2011; 127:589-94. [DOI: 10.1016/j.thromres.2011.01.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 01/18/2011] [Accepted: 01/31/2011] [Indexed: 12/15/2022]
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van den Besselaar AMHP, Witteveen E, Tripodi A. Calibration of combined thromboplastins with the International Standard for Thromboplastin, rabbit, plain. J Thromb Haemost 2011; 9:881-2. [PMID: 21261807 DOI: 10.1111/j.1538-7836.2011.04219.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tripodi A, Chantarangkul V, Van Den Besselaar AMHP, Witteveen E, Hubbard AR. International collaborative study for the calibration of a proposed international standard for thromboplastin, human, plain. J Thromb Haemost 2010; 8:2066-8. [PMID: 20626621 DOI: 10.1111/j.1538-7836.2010.03980.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- A Tripodi
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Centre, Department of Internal Medicine, Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico and Università degli Studi di Milano, Milan, Italy.
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van den Besselaar A, Chantarangkul V, Tripodi A. Effect of prothrombin time outlier exclusion rules on ISI calibration in multicentre studies. Thromb Res 2010; 125:523-8. [DOI: 10.1016/j.thromres.2010.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 12/11/2009] [Accepted: 01/11/2010] [Indexed: 01/21/2023]
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van den Besselaar AMHP, Chantarangkul V, Tripodi A. Thromboplastin standards. Biologicals 2010; 38:430-6. [PMID: 20338779 DOI: 10.1016/j.biologicals.2010.02.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 02/11/2010] [Indexed: 12/26/2022] Open
Abstract
The Prothrombin Time (PT) test is used for monitoring of treatment with Vitamin K-antagonists (VKA). The result of the PT test should be expressed as the International Normalized Ratio (INR). Calculation of INR is based on the availability of International Standards (IS) for thromboplastin and a calibration model. Calibration of a new PT test system is performed with the appropriate IS and fresh plasma samples of healthy (normal) volunteers and patients treated with VKA. The calibration model is based on the assumption of a linear relationship between the log(PT)'s obtained with the new PT system and the reference IS for both normal and patients' samples. Patients' samples for calibration should be selected by rejecting samples beyond the 1.5-4.5 INR range. Outliers should be rejected defined as points with a perpendicular distance greater than three residual standard deviations from the line of relationship. Selection of patients' samples and rejection of outliers result in a reduction of the between-laboratory variation of calibration. In addition to monitoring of VKA, the PT is used for management of patients with chronic liver disease. Likewise, INR(liver) should be based on calibration with an IS using samples from patients with chronic liver disease.
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van den Besselaar AMHP, Hubbard AR, Tripodi A. Continuation of the international standard thromboplastin (human, recombinant, plain) by means of a replacement reconstitution fluid. J Thromb Haemost 2008; 6:1042-3. [PMID: 18363819 DOI: 10.1111/j.1538-7836.2008.02962.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tripodi A, Chantarangkul V, Mannucci PM. The international normalized ratio to prioritize patients for liver transplantation: problems and possible solutions. J Thromb Haemost 2008; 6:243-8. [PMID: 17988228 DOI: 10.1111/j.1538-7933.2008.02827.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The prothrombin time (PT) test once designed by Dr Quick to investigate patients with obstructive jaundice was later adapted and standardized by means of the international normalized ratio (INR) to monitor patients on treatment with vitamin K antagonists (VKA). After more than 70 years from its introduction it is now time to think about its standardization for those very patients for whom it was intended at the beginning of its history. Two studies carried out independently and published recently in the same issue of a specialized journal do exploit the very same idea on how to accomplish this standardization. Both of them confirm previous anecdotal observations that the INR as devised for patients on VKA (INR(vka)) is not valid to harmonize PT results for patients with chronic liver disease. This fact, that at first sight may appear academic, has important consequences because the PT INR is used to construct the model for end-stage liver disease (MELD) scores, which is widely used to prioritize patients for liver transplantation. The two studies further demonstrate that an alternative calibration model, modified from that recommended by the World Health Organization for patients on VKA, may be feasible also for patients with chronic liver disease. This alternative calibration model, which calls for the substitution of plasmas from patients on VKA with those from patients with chronic liver disease, may be highly beneficial to harmonize the calculation of the MELD score, with important implications for the prioritization of patients for liver transplantation.
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Affiliation(s)
- A Tripodi
- Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine and Medical Specialties, University and IRCCS Maggiore Hospital, Mangiagalli and Regina Elena Foundation, Milan, Italy.
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van den Besselaar AMHP, Tripodi A. Effect of daptomycin on prothrombin time and the requirement for outlier exclusion in International Sensitivity Index calibration of thromboplastin. J Thromb Haemost 2007; 5:1975-6. [PMID: 17723138 DOI: 10.1111/j.1538-7836.2007.02679.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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