[1] Univ Penn, Sch Med, Dept Med, Div Gen Internal Med, Philadelphia, PA 19104 USA
[2] Philadelphia Vet Affairs Med Ctr, Ctr Hlth Equ Res & Promot, Dept Vet Affairs, Philadelphia, PA USA
[3] Pittsburgh Vet Affairs Hlth Care Syst, Pittsburgh, PA USA
[4] Univ Penn, Leonard Davis Inst Hlth Econ, Philadelphia, PA 19104 USA