[1] Univ Washington, Dept Surg, Surg Outcomes Res Ctr, Seattle, WA 98195 USA
[2] Univ Washington, Dept Biostat, Seattle, WA 98195 USA
[3] Kaiser Permanente, Northern Calif, Oakland, CA USA
[4] Henry Ford Hlth Syst, Detroit, MI USA
[5] Univ Washington, Dept Radiol, Comparat Effectiveness Cost & Outcomes Res Ctr, Seattle, WA 98195 USA
[6] Univ Washington, Dept Hlth Serv, Seattle Qual Life Grp, Seattle, WA 98195 USA