The Impact of Chronic Skin Disease on Daily Life (ISDL): a generic and dermatology-specific health instrument

Abstract

In dermatological research and clinical practice, there is a need for comprehensive self-report instruments that assess a broad spectrum of health implications of chronic skin diseases, including generic and skin-specific aspects of disease-related quality of life. The advantages of dermatology-specific, multidimensional instruments over generic instruments or single-dimensional quality-of-life measures are in the detailed and specific information they provide about health areas that are affected by the skin condition and that may change through therapeutic intervention. The development of a multidimensional health status inventory for chronic skin diseases (Impact of Chronic Skin Disease on Daily Life, ISDL) is described. The dermatology-specific part of the inventory assesses dimensions of physical functioning, more specifically skin status, physical symptoms of itch, pain and fatigue and scratching responses as well as disease-related stressors like stigmatization. The generic part gauges dimensions of psychological functioning, disease-related impact, illness cognitions and social support by means of existing scales validated for other chronic diseases. Reliability and validity of the questionnaire were studied in various samples of patients with psoriasis and atopic dermatitis. The ISDL showed high reliability and test-retest reliability in both patient groups. Convergent validity was indicated by moderate to strong correlations with other validated questionnaires. The scales proved sensitive to change both for dermatological ultraviolet B radiation therapy and cognitive behavioural treatment for itching. With its convincing results for reliability and validity the present evaluation supports the usefulness and applicability of the instrument for different chronic skin diseases.