The psoriasis family index: preliminary results of validation of a quality of life instrument for family members of patients with psoriasis.

BACKGROUND: Psoriasis can have a major impact on the lives of patients, the members of their families and their partners.
OBJECTIVES: To develop and validate a disease-specific instrument to measure the secondary impact of psoriasis on the health-related quality of life (HRQoL) of family members of psoriasis patients.
METHODS: The development of the new questionnaire involved a number of different stages: qualitative interviews with family members/partners, formulation of the first draft, refinement, initial validation, further refinement and finally revalidation of the questionnaire.
RESULTS: Items for the measure were generated from the content analysis of interview transcripts. The psychometric evaluation of the final draft of the Psoriasis Family Index (PFI-15) was carried out in a new cohort of participants. The PFI-15 demonstrated high internal consistency (Cronbach's alpha = 0.86) and high test-retest reliability (intraclass correlation coefficient = 0.93). The construct validity was assessed by testing a number of a priori hypotheses about its construct; a moderate to strong correlation was seen between families' PFI scores and patients' Dermatology Life Quality Index scores (r = 0.54, p < 0.01) and Psoriasis Disability Index scores (r = 0.59, p < 0.01), and between families' PFI scores and patients' Psoriasis Area and Severity Index scores (r = 0.43, p < 0.01).
CONCLUSIONS: The PFI is a simple and practical measure to assess the HRQoL of family members/partners of patients with psoriasis. 2009 S. Karger AG, Basel.