The Psoriasis Disability Index questionnaire is designed for use in adults, i.e. patients over the age of 16. It is self explanatory and can be handed to the patient who is asked to fill it in without the need for a detailed explanation. It is usually completed in three or four minutes.
There are two possible alternative formats of the PDI. One uses visual analogue scales for each answer, the other uses tick box choices for each answer.
Scoring (Visual Analogue Scale)
The scoring of each question is answered on a graded scale from 0 - 6. If a question is left unanswered the score taken is 0. The PDI is calculated by summing the score of each of the fifteen questions resulting in a maximum of 90 and a minimum of 0. The higher the score, the more quality of life is impaired. The PDI can also be expressed as a percentage of the maximum possible score of 90.
Scoring (Tick-box method)
The scoring of each question is answered on a series of 4 answers; not at all (scores 0), a little (scores 1), a lot (scores 2), very much (scores 3). If a question is left unanswered the score taken is 0. The PDI is calculated by summing the score of each of the 15 questions resulting in a maximum of 45 and a minimum of 0. The higher the score, the more quality of life is impaired. The PDI can also be expressed as a percentage of the maximum possible score of 45.
Detailed analysis of the PDI (second version)
The PDI can be analysed under five headings as follows:
| VAS | Tick-Box | ||
| Daily Activities | Questions 1, 2, 3, 4 and 5 | Score max 30 | 15 |
| Work or School or alternative questions | Question 6, 7 and 8 | Score max 18 | 9 |
| Personal relationships | Questions 9 and 10 | Score max 12 | 6 |
| Leisure | Questions 11, 12, 13 and 14 | Score max 24 | 12 |
| Treatment | Question 15 | Score max 6 | 3 |
The scores for each of these sections can also be expressed as a percentage of the maximum score for each section.
References
1. Finlay AY, Kelly SE. Psoriasis: an index of disability. Clin Exper Derm, 1987; 12: 8-11. (Gives text of original version)
2. Finlay AY, Khan GK, Luscombe DK, Salek MS. A validation of Sickness Impact Profile and Psoriasis Disability Index in Psoriasis. Brit J Dermatol, 1990; 123: 751-756. (Second version)
3. Finlay AY, Coles EC. The effect of severe psoriasis on the quality of life of 369 patients. Brit J Dermatol, 1995; 132: 236-244. (Gives text of current (second) version)
4. Lewis VJ, Finlay AY. Two Decades Experience of the Psoriasis Disability Index. Dermatology, 2005, 210:261-268.
Please note that the Psoriasis Disability Index (PDI) is protected under copyright. However, permission is usually given for the PDI to be used for research purposes.
The copyright statement:
© Psoriasis Disability Index. A Y Finlay, S E Kelly 1985
This statement must always be reproduced at the end of every copy of the PDI.
The PDI may be used for routine clinical use by clinicians in order to assist the clinical consultation, evaluation and clinical decision making process. There is no need to seek specific permission for this and there is no charge for the use of the PDI. However it is a requirement that every copy of the PDI, in whatever language, should always reprint the copyright statement at the end of the PDI.
For general queries, technical aspects and permission to use:
E-mail: dermqol@cf.ac.uk
Other contacts:
Mrs Joy Hayes (financial aspects): HayesJ@cf.ac.uk
Professor Andrew Y Finlay: FinlayAY@cf.ac.uk
Address:
Department of Dermatology
Cardiff University School of Medicine
Heath Park, Cardiff
CF14 4XN
United Kingdom
Te: +44 (0)29 2074 2884
Fax: +44 (0)29 2074 4321