[1] QCMetrix Inc, Waltham, MA 02451 USA
[2] Univ Virginia, Dept Surg, Charlottesville, VA USA
[3] Massachusetts Gen Hosp, Dept Surg, Codman Ctr Clin Effectiveness Surg, Boston, MA 02114 USA
[4] Harvard Univ, Sch Med, Boston, MA USA
[5] Brigham & Womens Hosp, Boston, MA 02115 USA
[6] VA Boston Healthcare Syst, West Roxbury, MA USA
[7] Univ Colorado Hlth Outcomes Program, Aurora, CO USA