[1] Stavanger Univ Hosp, Dept Dermatol, Stavanger, Norway
[2] Stavanger Univ Hosp, Sect Biostat, Res Dept, Stavanger, Norway
[3] Stavanger Univ Hosp, Dept Internal Med, Clin Immunol Unit, POB 8100, N-4068 Stavanger, Norway
[4] Univ Bergen, Dept Clin Sci, Fac Med, Bergen, Norway