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

Background: 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.

Objectives: 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.

Methods: Reliability and validity of the questionnaire were studied in various samples of patients with psoriasis and atopic dermatitis.

Results: 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.

Conclusion: With its convincing results for reliability and validity the present evaluation supports the usefulness and applicability of the instrument for different chronic skin diseases.