[1] Tufts Univ, Sch Med, Dept Med, Boston, MA 02111 USA
[2] Univ Washington, Sch Publ Hlth & Community Med, Dept Hlth Serv, Seattle, WA 98195 USA
[3] Tufts Med Ctr, Inst Clin Res & Hlth Policy Studies, Hlth Inst, Boston, MA USA
[4] Blue Cross & Blue Shield Massachusetts, Boston, MA USA