Outcome revealed by preference in schizophrenia (OPS): development of a new class of outcome measurements

The objective of this paper is to describe the development of a new type of outcome measurement, based on revealed preference, which can be used in serious chronic illnesses. Fifteen texts of about 200 words each were written by one of the authors on the day-to-day life of 15 schizophrenic patients. These 15 'slices of life' thus described were then ranked in terms of acceptability by a second group of 10 schizophrenic patients and by a group of 12 relatives of schizophrenic patients. From these rankings, six situations were selected so as to obtain evenly distributed positioning on an axis of acceptability. These six situations comprised the final instrument. In administration, the patients were first asked if the 'slices of life' that were described were acceptable or not, then if the 'slices of life' described were more or less acceptable than their own lives. Two scores were derived, one for an absolute level and the other for a relative level of the patient's satisfaction with his or her existence. Validation results were presented to a new sample of 229 schizophrenic patients. Internal consistency appeared good and the initial ranking of the six situations in terms of acceptability was confirmed. This study encourages the development of global outcome measures based on revealed preference in chronic serious illnesses.