1. From the Gaubius Laboratory (V.v.W., L.S., M.M.L.D., M.R.d.V., J.S., A.S., D.E., P.H.A.Q.), TNO Quality of Life, Leiden, the Netherlands; and the Departments Surgery (V.v.W., A.S., D.E., J.H.v.B., P.H.A.Q.), Rheumatology (R.E.M.T.), and Medical Statistics (P.H.E.), Leiden University Medical Center (LUMC), Leiden, the Netherlands, and Laboratory for Physiology, ICAR-VU, VU University Medical Center, Amsterdam, the Netherlands (L.S., V.W.M.v.H.).