[1] Univ N Carolina, Sch Med, Dept Med, Div Gen Med & Clin Epidemiol, Chapel Hill, NC 27515 USA
[2] Univ N Carolina, Cecil G Sheps Ctr Hlth Serv Res, Chapel Hill, NC 27515 USA
[3] Univ Michigan, Div Gen Med, Ann Arbor, MI 48109 USA
[4] Vet Affairs Ann Arbor Healthcare Syst, Ctr Clin Management Res, Ann Arbor, MI USA
[5] Stanford Univ, Ctr Primary Care & Outcomes Res, Ctr Populat Hlth Sci, Dept Med, Palo Alto, CA 94304 USA
[6] Stanford Univ, Ctr Primary Care & Outcomes Res, Ctr Populat Hlth Sci, Dept Hlth Res & Policy, Palo Alto, CA 94304 USA
[7] Harvard Med Sch, Ctr Primary Care, Boston, MA USA