[1] Univ Western Ontario, Div Nephrol, London, England
[2] Univ Alberta, Div Nephrol, Edmonton, AB, Canada
[3] Inst Hlth Econ, Edmonton, AB, Canada
[4] Univ Western Ontario, Dept Polit Sci, London, ON, Canada
[5] Univ Western Ontario, Dept Epidemiol & Biostat, London, ON, Canada
[6] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada