[1] MCMASTER UNIV, HLTH SCI CTR, DEPT MED, HAMILTON, ON L8N 3Z5, CANADA
[2] MCMASTER UNIV, HLTH SCI CTR, DEPT CLIN EPIDEMIOL & BIOSTAT, HAMILTON, ON L8N 3Z5, CANADA
[3] JOHNS HOPKINS UNIV, SCH MED, DIV INTERNAL MED, BALTIMORE, MD USA
[4] US CONGRESS, OFF TECHNOL ASSESSMENT, HLTH PROGRAM, WASHINGTON, DC USA
[5] WAKE FOREST UNIV, BOWMAN GRAY SCH MED, DEPT MED, WINSTON SALEM, NC USA