[1] Nordland Hosp, Dept Lab Med, Bodo, Norway
[2] Univ Tromso, Fac Hlth Sci, N-9001 Tromso, Norway
[3] Univ Penn, Dept Pathol & Lab Med, Perelman Sch Med, Philadelphia, PA 19104 USA
[4] Univ Oslo, Rikshosp, Oslo Univ Hosp, Inst Immunol, N-0027 Oslo, Norway