Validation of the Weiss Functional Impairment Rating Scale (WFIRS-P) as a Functional Impairment Measure in a General Population of Schoolchildren.

Functional impairment rating scales are few in numbers and have mainly been examined in clinical populations. The Weiss Functional Impairment Rating Scale-Parent report (WFIRS-P) is a case in point. We tested the psychometric properties of the WFIRS-P in the largest general population study to date and for the first time examined the factor structure of the scale in a general population setting. Participants were 2,027 schoolchildren aged 6 to 11. Parents/caregivers completed the WFIRS-P and criterion measures of quality of life, attention-deficit/hyperactivity disorder, and behavioral/emotional symptoms. Confirmatory factor analysis and convergent/divergent validity analyses supported a six-factor structure: family, life skills, self-concept, social activities, and the separation of the school domain into two smaller domains covering school learning and school behavior. Children with and without a history of referral differed significantly on all six domains supporting the external validity. In conclusion, the WFIRS-P was found to generate valid scores in a general population sample.