[1] Ostfold Hosp Trust, Dept Cardiol, POB 300, N-1714 Gralum, Norway
[2] Univ Oslo, Inst Clin Med, POB 1171, N-0318 Oslo, Norway
[3] NTNU Norwegian Univ Sci & Technol, Fac Med & Hlth Sci, HUNT Res Ctr, Forskningsveien 2, N-7600 Levanger, Norway
[4] Ostfold Hosp Trust, Dept Haematol, POB 300, N-1714 Gralum, Sarpsborg, Norway
[5] Statisticon AB, Klara Sodra Kyrkogata 1, S-11152 Stockholm, Sweden
[6] Oslo Univ Hosp Ulleval, Dept Cardiol, POB 4956, NO-0424 Oslo, Norway