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.