[1] Karolinska Univ Hosp, Dept Med, Div Hematol, Stockholm, Sweden
[2] Karolinska Inst, Stockholm, Sweden
[3] Univ Iceland, Fac Med, Reykjavik, Iceland
[4] Univ Iceland, Dept Hematol, Reykjavik, Iceland
[5] Landspitali Natl Univ Hosp, Reykjavik, Iceland
[6] Karolinska Inst, Dept Med Epidemiol & Biostat, Stockholm, Sweden