Objective: To refine and validate the Parental Illness Impact Scale (PIIS), a questionnaire designed specifically to measure the quality of life of adolescent and adult children of neurologically affected parents.
Methods: Key informant interviews and a literature review were conducted to ensure all relevant themes were incorporated in the revised PIIS (PIIS-R). Pre-testing was achieved through a 17 member expert panel and cognitive interviews with eight adolescent and adult children. The revised instrument was administered to 169 adolescent and adult children of people with Parkinson's disease, multiple sclerosis and stroke and subjected to psychometric analysis.
Results: Principal components analysis resulted in eight subscales accounting for 60.6% of explained variance. The PIIS-R showed good concurrent and discriminant validity through correlations with established measures of quality of life and psychosocial well-being. Internal consistency was high (Cronbach's alpha .92), and test-retest reliability values for subscales (r = .59-.74) and total score (r = .79) were moderate to high.
Conclusions: The PIIS-R is a scientifically robust measurement tool for assessing the impact of parental illness, and currently shows strong psychometric properties. Longitudinal data will be required to assess predictive validity and sensitivity to change. The instrument is available to other investigators, who are encouraged to further evaluate its scientific properties.
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