[1] Northwestern Univ, Sch Med, Div Gen Internal Med, Chicago, IL 60611 USA
[2] Blue Cross & Blue Shield Assoc, Technol Evaluat Ctr, Chicago, IL USA
[3] Hines VA Med Ctr, Midwest Ctr Hlth Serv & Policy Res, Hines, IL USA
[4] Amer Med Assoc, Chicago, IL 60610 USA
[5] Univ Michigan, Sch Publ Hlth, Ann Arbor, MI 48109 USA