[1] Hosp Sick Children, Div Nephrol, Toronto, ON, Canada
[2] Univ Toronto, Dept Paediat, Toronto, ON, Canada
[3] Hosp Sick Children, Res Inst, Child Hlth Evaluat Sci, Toronto, ON, Canada
[4] Womens Coll Hosp, Dept Med, Toronto, ON, Canada
[5] Univ Toronto, Interdept Div Crit Care Med, Toronto, ON, Canada
[6] Sunnybrook Hlth Sci Ctr, Res Inst, Toronto, ON, Canada
[7] Sunnybrook Hlth Sci Ctr, Dept Crit Care Med, Toronto, ON, Canada
[8] Univ Toronto, Dalla Lana Sch Publ Hlth, Div Biostat, Toronto, ON, Canada
[9] UCL, Dept Stat Sci, London, England