[1] Univ Calif Los Angeles, David Geffen Sch Med, Los Angeles, CA 90095 USA
[2] MedStar Georgetown Surg Outcomes Res Ctr, Washington, DC USA
[3] MedStar Hlth Res Inst, Washington, DC USA
[4] MedStar Georgetown Univ Hosp, Dept Surg, Washington, DC USA
[5] MedStar Integrated Surg Serv, Baltimore, MD USA