The Psoriasis Disability Index (PDI) was written by A Y Finlay and S E Kelly and first published in 1987 (copyright 1985). This guide explains who it is for, how it is scored, what the scores mean, the research behind it, and how to get it and license it.
The short answer
The Psoriasis Disability Index (PDI) measures disability and quality-of-life impairment caused by psoriasis. It is for adults aged 16 and over, has 15 questions, asks about four weeks, and gives a total score from 0 to 45. Cardiff's page does not publish score bands for it.
Table of Contents
How the PDI is scored
Each answer is scored as follows: Very much 3, A lot 2, A little 1, Not at all 0, unanswered 0. The answers are added together to give a total from 0 to 45. Higher scores mean a bigger impact on quality of life.
Respondents should complete it on their own, without being guided towards any answer, and the score numbers must not be printed next to the answer options. Under Cardiff’s general guidance, a questionnaire with one unanswered question can still be scored, but two or more unanswered questions make it invalid.
Who the PDI is for
Adults aged 16 and over.
Authors: A Y Finlay and S E Kelly. First published: 1987 (copyright 1985). Original paper: Finlay AY, Kelly SE. Clin Exp Dermatol 1987;12:8-11.
Copyright statement: © Psoriasis Disability Index. A Y Finlay, S E Kelly 1985. By agreement, Cardiff University now owns and administers the copyright.
Language versions: 24 languages (Arabic, Bosnian, Chinese, Czech, Danish, Filipino, Finnish, French, German, Gujarati, Hindi, Icelandic, Italian, Japanese, Lithuanian, Marathi, Portuguese, Romanian, Serbian, Spanish, Thai, Turkish, Ukrainian, Zulu).
Research and validation
- 369 patients with severe psoriasis (Finlay AY, Coles EC. Br J Dermatol 1995;132:236-244; gives the current second version)
- Validation vs Sickness Impact Profile (Finlay AY et al. Br J Dermatol 1990;123:751-756)
- Two decades of experience (Lewis VJ, Finlay AY. Dermatology 2005;210:261-268)
How to get the PDI and when you need a licence
Patients and clinicians can use the PDI, in any available language, for routine clinical care without a licence and at no charge. It can be downloaded from Cardiff University’s PDI page. Data collected as part of routine care can also be analysed and published without a licence.
Students need a free licence, which must be requested by a member of staff at their institution, usually the research or medical supervisor, through Cardiff’s online form. A separate licence is needed for each questionnaire.
There is no fee for the PDI, but you still need a licence for anything other than routine clinical use. Apply by emailing Cardiff’s Technology Transfer office (technologytransfer@cardiff.ac.uk); the online licensing form does not cover it.
The wording, format and question order cannot be changed. Electronic versions need Cardiff’s formal permission, and the copyright statement must stay visible.
Related questionnaires
The PDI is one of a family of quality-of-life measures developed at Cardiff University. See the full guide to dermatology quality of life questionnaires, or the individual guides: DLQI · CDLQI · FDLQI · IDQOL · CADI · DFI.
To score how much psoriasis is on the skin, rather than its effect on daily life, use our PASI score calculator.
Frequently asked questions
What does the PDI measure?
Who is the PDI for?
How is the PDI scored?
Is the PDI free to use?