OBJECTIVES: Patient-reported outcomes (PROs) are necessary to assess disease impacts from the patient's perspective. In line with the Food and Drug Administration’s (FDA’s) guidance on PROs, the Depression and Family Functioning Scale (DFFS) was developed to assess the impact of major depressive disorder (MDD) on family functioning. Psychometric analyses were conducted to establish the reliability, validity, and responsiveness of the DFFS according to the FDA PRO guidance.
METHODS: Data from PERFORM, a longitudinal multicenter, prospective, 2-year observational study in the United Kingdom and Spain, were analyzed (NBaseline= 478; NMonth2= 433). The 15 DFFS items use a 5-point rating scale to assess partner and family interactions and quality of relationships; higher scores indicate greater (worse) impacts. Test-retest reliability (intraclass correlations), construct validity (correlations and factor analysis), discriminating ability (analyses of variance), and responsiveness (effect size estimates) were evaluated.
RESULTS: Factor analyses resulted in a single factor, confirmed by highly satisfactory Cronbach’s alphas (0.85 at baseline, 0.89 at month 2). The DFFS demonstrated satisfactory test-retest reliability (intraclass correlation= 0.75). Hypothesized correlations with other measures provided evidence of convergent and divergent validity. For example, the correlation of the DFFS with SF-12 mental component scores was -0.35 (baseline) -0.49 (month 2), and with SF-12 physical component scores, -0.05 (baseline) and -0.31 (month 2). Hypothesis tests were generally in the predicted direction and many were statistically significant, substantiating the discriminating ability of the DFFS. Effect size estimates of responsiveness were 0.44–0.84, demonstrating that the items were capable of detecting change.
CONCLUSIONS: The psychometric analyses strongly support the reliability, validity, and responsiveness of the DFFS and its usefulness for assessing the impacts of depression on family functioning. It has the potential to provide important information not traditionally captured in clinical practice or research and will facilitate a more comprehensive evaluation of treatments of MDD.
