[1] Ullevaal Univ Hosp, Oslo, Norway
[2] Sahlgrens Univ Hosp, Gothenburg, Sweden
[3] Cornell Univ, Med Ctr, New York Hosp, New York, NY 10021 USA
[4] Univ Michigan, Med Ctr, Ann Arbor, MI USA
[5] Karolinska Univ Hosp, Stockholm, Sweden
[6] Univ Helsinki, Cent Hosp, Helsinki, Finland
[7] Glostrup Univ Hosp, Glostrup, Denmark
[8] MRL Scandinavia, Stockholm, Sweden
[9] Viborg Hosp, Viborg, Denmark
[10] Umea Univ, Umea, Sweden
[11] Haukeland Hosp, N-5021 Bergen, Norway
[12] Univ Alabama Birmingham, Med Ctr, Birmingham, AL 35294 USA
[13] Nordic Sch Publ Hlth, Gothenburg, Sweden