[1] Univ Toronto, Hosp Sick Children, Div Rheumatol, Toronto, ON M5G 1X8, Canada
[2] Univ Toronto, Dept Pediat Hlth Policy Management & Evaluat, Toronto, ON M5G 1X8, Canada
[3] Univ Toronto, Dept Publ Hlth Sci, Toronto, ON M5G 1X8, Canada
[4] Univ Colorado, Hlth Sci Ctr, Dept Pediat, Mt States Reg Hemophilia & Thrombosis Ctr, Denver, CO 80262 USA
[5] Univ Lund Hosp, Dept Radiol, Lund, Sweden
[6] Hosp Sick Children, Dept Diagnost Imaging, Toronto, ON M5G 1X8, Canada
[7] Malmo Univ Hosp, Dept Paediat, Malmo, Sweden
[8] Malmo Univ Hosp, Dept Coagulat Disorders, Malmo, Sweden
[9] Hosp Sick Children, Div Haematol Oncol, Toronto, ON M5G 1X8, Canada
[10] Univ Toronto, Dept Pediat, Toronto, ON M5G 1X8, Canada