Semin Vasc Med 2003; 03(3): 243-254
DOI: 10.1055/s-2003-44460
Copyright © 2003 by Thieme Medical Publishers, Inc., 333 Seventh Avenue, New York, NY 10001, USA. Tel.: +1(212) 584-4662

Oral Anticoagulant Monitoring by Laboratory or Near-Patient Testing: What a Clinician Should Be Aware Of

A. Tripodi1 , W. G.M. Breukink-Engbers2 , A. M.H.P. van den Besselaar3
  • 1Bonomi Hemophilia and Thrombosis Centre, University and IRCCS Maggiore Hospital, Milan, Italy
  • 2AntiStollingsCentrum Oost-Nederland (ASCON), Lichtenvoorde, The Netherlands
  • 3Department of Haematology, Haemostasis and Thrombosis Research Centre, Leiden University Medical Centre, Leiden, The Netherlands
Further Information

Publication History

Publication Date:
21 November 2003 (online)


Prothrombin time (PT) is the primary laboratory test for monitoring oral anticoagulant treatment but is influenced by preanalytical conditions and analytical variables, that is, thromboplastin reagents and instrumentation. Standardization and normalization of test results is mandatory. PT results should be transformed to International Normalized Ratio (INR) by calibration of the reagent/instrument system with International Reference standards according to World Health Organization guidelines. However, there is still uncertainty in the INR that is caused in part by calibration errors and in part by interaction between the PT reagent and various factors in the patient's specimen. These problems are highlighted in INR measurements performed with whole blood coagulation monitors. Each center should maintain an appropriate scheme of internal and external quality control for the laboratory INR measurement as well as the individual point-of-care coagulation monitors used by the center and patients for self-testing.


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