[1] Univ British Columbia, St Pauls Hosp, Div Gen Internal Med, Dept Med,Ctr Hlth Evaluat & Outcome Sci, Vancouver, BC V6Z 1Y6, Canada
[2] DM STAT Inc, Medford, MA USA
[3] Boston Univ, Sch Med, Dept Med, CARE Unit,Sect Gen Internal Med, Boston, MA 02215 USA
[4] Boston Univ, Sch Publ Hlth, Boston, MA 02215 USA
[5] Boston Univ, Sch Med, Dept Social & Behav Sci, Boston, MA 02215 USA
[6] Boston Univ, Sch Med, Dept Biostat, Boston, MA 02215 USA