Sample size According to sample size calculations we will include a total of N = 450 patients. N = 120 of these patients will be asked to fill in the questionnaires at a second time point, of which a subgroup of n = 60 will be subjected to test-retest analyses (patients who are clinically stable and indicate no change on an anchor question over the two assessment points), and another n = 60 will be subjected to test-retest analyses (those who indicate a change to the worse or to the better).