Finlay and Kelly developed the Psoriasis Disability Index (PDI) to evaluate the level of disability in a patient with psoriasis. The index was derived from an original list of 28 items covering daily activities, work, personal relationships, leisure and treatment. It can be monitored over time in conjunction with the change in the extent of the skin lesions. The authors are from Glasgow, Scotland.
NOTE: This describes the initial 10-item PDI. A 15-item index was referred to by Finlay et al (1990) and Kent and Al-Abadie (1993) but the items were not listed.
The instrument consists of 10 questions about disorder over the past 4 weeks .
Level of Disability
Points
none
1
minimal disability
2
mild disability
3
mild-to-moderate disability
4
moderate disability
5
severe disability
6
maximum (extreme) disability
7
PDI =
= SUM(points for all 10 questions)
Interpretation:
• minimum score: 0
• maximum score: 70
• The higher the PDI, the more severe the disability.
• Kent and Al-Abadie used factor analysis to demonstrate that the index consists of 2 subscales – one for everyday activities and one for communal activities.
Performance:
• The total area of skin involvement by psoriasis is not a reliable guide to disability.
• The PDI correlates well with the PASI score.
• The PDI has been used to quantitate the benefit of therapy (in patient topical).
• While developed for psoriasis, the index has been used for other skin conditions with minor modifications.
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