[1] Harvard Med Sch, Boston, MA USA
[2] Cambridge Hlth Alliance, Dept Med, Cambridge, MA USA
[3] Univ York, Hull York Med Sch, Hlth Profess Educ Unit, York, England
[4] Brigham & Womens Hosp, Dept Med, Boston, MA USA
[5] Cambridge Hosp, Cambridge Hlth Alliance, Dept Med, 1493 Cambridge St, Cambridge, MA 02138 USA