2 Centre for Metrological Traceability in Laboratory Medicine (CIRME), University of Milan, Milano, Italy.
3 Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, USA.
4 Department of Pathology, University of Maryland School of Medicine, Baltimore, MD, USA.
5 HyTest Ltd, Turku, Finland.
6 Analytical Science Group, National Physical Laboratory, Teddington, UK.
7 European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel, Belgium.
8 Biochemical Science Division, National Institute of Standards and Technology, Gaithersburg, MD, USA.
9 Pathology Queensland, Department of Chemical Pathology, Royal Brisbane and Women's Hospital, Herston, Qld, Australia. Electronic address: jill_tate@health.qld.gov.au.