Two decades experience of the Psoriasis Disability Index

The Psoriasis Disability Index (PDI) was formed 20 years ago. Since its introduction it has been used widely as a tool for assessment of quality of life in psoriasis. This paper reviews its use in 23 peer-reviewed articles and over 35 published abstracts, and describes its use in conjunction with other general and psoriasis-specific quality of life assessments, and with a range of physical and psychological measures. The PDI is effective in demonstrating the effects of interventions, both of treatments and in health service research. The PDI has been translated into at least 16 languages and has been used in published research in 20 countries.