Evaluation of the factor structure of the Child Obsessive-Compulsive Impact Scale - Revised (COIS-R) in Scandinavia with confirmatory factor analysis

Research on functional impairment in obsessive-compulsive disorder (OCD) based on standardized measurement lags behind compared to its prominence in diagnostic classification systems. Our aim was to evaluate the psychometric properties of the Child Obsessive Compulsive Impact Scale - Revised (COIS-R), which is a measure of OCD-related functional impairment. The sample consisted of 396 Danish, Swedish, and Norwegian youth diagnosed with OCD according to the Diagnostic and Statistical Manual of Mental Disorders (4th edition) (48.9% boys; mean age 12.9, SD=2.7). We used confirmatory factor analysis to evaluate the initial four-factor structure of the parent-reported measure (Daily Living Skills, School, Social, Family/Activities) and the three-factor structure of the child-reported measure (School, Social, Activities). We used the robust weighted least squares mean- and variance-adjusted estimator as applied in the MPLUS program (version 7.2). The parent-report format showed acceptable fit and the structure was equivalent across gender, age, and country. The child-report format showed poor fit and equivalent results across gender, age, and country. These findings indicate that the fit for the COIS-R original factor structure was acceptable for the parent-report but not for the child-report. The measure would benefit from revisions such as split sample procedure factor analyses with a large cross-cultural sample.