aDepartment of Medicine, St Michael's Hospital bDepartment of Physiology cDepartment of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada Correspondence to Dominic S. Ng, Department of Medicine, St Michael's Hospital, University of Toronto, Toronto, Ontario, Canada. Tel: +1 416 864 5197; fax: +1 416 864 5584; e-mail: [email protected]