1. Sunnybrook Health Sciences Centre, University of Toronto, Canada (D.T.K., M.J.S., H.C.W., J.V.T.)
2. Institute for Clinical Evaluative Sciences, Toronto, Canada (D.T.K, P.C.A., M.J.S., H.C.W., J.V.T., M.E., M.K.).
3. Department of Family and Community Medicine, University of Toronto, Canada (N.D.D.)
4. Center for Outcomes Research and Evaluation, Yale-New Haven Hospital, New Haven, CT (J.S.R., H.M.K.).