[1] Sykehuset Innlandet Hosp Trust, Dept Internal Med, Gjovik, Norway
[2] Univ Oslo, Fac Med, Inst Hlth & Soc, N-0316 Oslo, Norway
[3] Amer Univ Beirut, Dept Internal Med, Beirut, Lebanon
[4] Oslo Univ Hosp, Dept Haematol, N-0450 Oslo, Norway
[5] Univ Oslo, Fac Med, Inst Clin Med, N-0316 Oslo, Norway
[6] McMaster Univ, Dept Clin Epidemiol & Biostat, Hamilton, ON, Canada