To evaluate the psychometric properties of a German modification of the Weiss Functional Impairment Rating Scale—Parent Report for children with aggressive and oppositional behavior problems (WFIRS-P for ODD/CD).
Data were collected from a clinical sample of children (6–12 years; 96% boys) with oppositional defiant disorder (ODD) and conduct disorder (CD) (N = 219). The WFIRS-P conceptual framework was evaluated using confirmatory factor analyses (CFA). Reliability was estimated using internal consistency (Cronbach’s alpha) and omega statistics. Validity was assessed through correlations between WFIRS-P for ODD/CD domain scores and parent-rated scales on symptoms of ODD, CD, attention-deficit/hyperactivity disorder (ADHD), a broad range of other behavioral and emotional problems, and scales on health-related quality of life and family burden.
CFA of the WFIRS-P for ODD/CD revealed that a bifactor model, with a general factor accounting for common variance (ωH = 0.23–0.48) and independent specific group factors accounting for additional variance in item scores (ωS = 0.37–0.60), best fits the data. Thus, CFA confirmed the theoretical assumption of a general construct of impairment (total scale) and additional specific impairments (subscales, e.g., family, social activities). Cronbach’s alpha coefficient exceeded 0.70 for all subscales. Omega statistics showed that both the general construct and specific factors accounted for item variance. As expected, correlations with symptoms scales for ODD/CD and ADHD were low to moderate.
The use of the parent-rated WFIRS for ODD/CD in identifying ODD- and CD-related impairment in children is psychometrically supported. The scale can be employed to assess functional impairment in children with aggressive behavior problems.