1. Department of Medicine, University of British Columbia, Vancouver, BC V5Z 1M9, Canada
2. Centre for Health Evaluation and Outcome Sciences, St. Paul’s Hospital, Vancouver, BC V6Z 1Y6, Canada
3. Centre for Research on Inner City Health, St. Michael’s Hospital, Toronto, ON M5B 1W8, Canada
4. Department of Medicine, University of Toronto, Toronto, ON M5G 2C4, Canada