Measuring quality of life in psoriasis: the CALIPSO questionnaire.

In dermatology, several instruments are available to measure health-related quality of life (HRQoL) of patients. They vary in content emphasis and in the extent to which their measurement properties have been investigated and reported. In this study, we summarized five dermatology- and psoriasis-specific HRQoL questionnaires into a new psoriasis-specific questionnaire, the Comprehensive Appraisal of Life Impact of PSOriasis (CALIPSO). The questionnaires were completed by 936 patients with a diagnosis of psoriasis. Rasch's unidimensional measurement model was used to verify the construct validity and the operational characteristics of each instrument separately. The items with the best performance according to the Rasch model were selected. The final 30 items constitute the CALIPSO. Responses are given on a 3-point scale: "never", "sometimes/quite frequently", "often/all the time". The properties of the CALIPSO now need to be verified through the analysis of new data from different populations of people with psoriasis. In future, clinicians may use it without having to decide amongst several competing scales, to evaluate HRQoL in patients with psoriasis.