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

Treatment with vitamin K antagonist (VKA) should be monitored to ensure safety and efficacy [ [1] Keeling D. Baglin T. Tait C. Watson H. Perry D. Baglin C. Kitchen S. Makris M. BCSH Guidelines on oral Anticoagulation with warfarin – 4th edition. BJH. 2011; 154: 31-324 Crossref Scopus (466) Google Scholar ]. This is usually done by determination of prothrombin time that is transformed into the international normalized ratio (INR) using the international sensitivity index (ISI), and mean normal prothrombin time [ [2] WHO Expert Committee on Biological StandardizationSixty-second report. Guidelines for thromboplastins and plasma used to control oral anticoagulant therapy with vitamin K antagonists. WHO Technical Report Series. 2013; 979: 273-305 Google Scholar ], so that results obtained by different methods are harmonized. World Health Organization (WHO) maintains international standards (IS) for thromboplastins of human and rabbit origin that have ISI assigned according to published guidelines [ [2] WHO Expert Committee on Biological StandardizationSixty-second report. Guidelines for thromboplastins and plasma used to control oral anticoagulant therapy with vitamin K antagonists. WHO Technical Report Series. 2013; 979: 273-305 Google Scholar ] to facilitate this process. The ISI of these IS are traceable back to the first IS for thromboplastin coded 67/40. When required, the calibration of replacement IS for thromboplastins should involve testing of candidates against all existing IS and the ISI assigned to the new IS should be the mean of ISIs obtained by calibration against all existing IS [ [2] WHO Expert Committee on Biological StandardizationSixty-second report. Guidelines for thromboplastins and plasma used to control oral anticoagulant therapy with vitamin K antagonists. WHO Technical Report Series. 2013; 979: 273-305 Google Scholar ]. The current IS for human thromboplastin is coded rTF 16 and was established by WHO in October 2016 [ [3] van den Besselaar A.M.H.P. Chantarangkul V. Angeloni F. Binder N.B. Byrne M. Dauer R. Gudmundsdottir B.R. Jespersen J. Kitchen S. Legnani C. Lindahl T.L. Manning R.A. Martinuzzo M. Panes O. Pengo V. Riddell A. Subramanian S. Szederjesi A. Tantanate C. Herbel P. et al. 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 Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar ]. It replaced the previous human IS coded rTF 09, which was established by WHO in 2009 [ [4] Tripodi A. Chantarangkul V. van den Besselaar A.M.H.P. Witteveen E. Hubbard A.R. subcommittee on Control of Anticoagulation of the SSC of the ISTH. International collaborative study for the calibration of a proposed international standard for thromboplastin, human, plain. J Thromb Haemost. 2010; 8: 2066-2068 Abstract Full Text Full Text PDF PubMed Scopus (14) Google Scholar ]. The current IS for rabbit thromboplastin is coded RBT 16 and was established by WHO in October 2016 [ [3] van den Besselaar A.M.H.P. Chantarangkul V. Angeloni F. Binder N.B. Byrne M. Dauer R. Gudmundsdottir B.R. Jespersen J. Kitchen S. Legnani C. Lindahl T.L. Manning R.A. Martinuzzo M. Panes O. Pengo V. Riddell A. Subramanian S. Szederjesi A. Tantanate C. Herbel P. et al. 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 Abstract Full Text Full Text PDF PubMed Scopus (16) Google Scholar ]. It replaced the previous rabbit IS-coded RBT 05, which was established by WHO in 2005 [ [5] Chantarangkul V. van den Besselaar A.M. Witteveen E. Tripodi A. International collaborative study for the calibration of a proposed international standard for thromboplastin, rabbit, plain. J Thromb Haemost. 2006; 4 (1339–45) Crossref Scopus (26) Google Scholar ].