1. Coagulation Reference Laboratory, Department of Clinical Chemistry and Laboratory Medicine , Leiden University Medical Center , P.O. Box 9600 , Leiden, 2300 RC , The Netherlands
2. Coagulation Reference Laboratory, Department of Clinical Chemistry and Laboratory Medicine , Leiden University Medical Center , Leiden , The Netherlands
3. National Institute for Biological Standards and Control , Potters Bar , UK
4. Sheffield Thrombosis and Haemostasis Centre, Royal Hallamshire Hospital , Sheffield , UK
5. IRCCS Cà Granda Maggiore Hospital Foundation, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa , Milano , Italy