[1] St Olavs Hosp, Rheumatolgy, Univ Hosp, NTNU, Trondheim, Norway
[2] Norwegian Univ Sci & Technol, Dept Publ Hlth & Nursing, Fac Med, NTNU, Trondheim, Norway
[3] Norwegian Univ Sci & Technol, Dept Publ Hlth & Nursing, Fac Med, NTNU, Trondheim, Norway
[4] Norwegian Univ Sci & Technol, NTNU, Trondheim, Norway
[5] Univ Calif San Diego, Med, La Jolla, CA 92093 USA