W. Garry John, Gunnar Nordin and Mauro Panteghini* 1 Clinical Biochemistry, Norfolk and Norwich University Hospital, and School of Medicine, Health Policy and Practice, UEA, Norwich, NR4 7UY, UK 2 External Quality Assurance in Laboratory Medicine in Sweden, Uppsala, Sweden 3 Centre for Metrological Traceability in Laboratory Medicine (CIRME) and Department of Clinical Sciences ‘‘Luigi Sacco’’, ...