Rasch analysis of the Developmental Test of Visual-Motor Integration in children with intellectual disabilities

The purpose of this study was to examine the measurement properties of the Developmental Test of Visual-Motor Integration (VMI) in children with intellectual disabilities (ID) ages 4-12 years using the dichotomous Rasch model. The VMI was administered individually to 454 children with ID. Rasch analysis was applied to investigate unidimensionality, item fit to the model, differential item functioning (DIF), and item targeting. Discriminative validity was obtained by receiver operating characteristic (ROC) curve analysis. Items were eliminated if the task was too easy or too difficult, or showed misfit to the Rasch model. The remaining items fitted the unidimensional construct the test was intended to measure and were free of DIF. The Rasch reduced version of the VMI with 9 items appeared to be suited to measure mild degrees of perceptual-motor impairment and demonstrated excellent reliability (0.91). VMI-9 had a larger area under the ROC curve in its ability to differentiate mild versus moderate to severe ID compared with the original version. Taken together, the VMI-9 provides a quick, reliable and valid measure for screening and identifying perceptual-motor deficits in children with ID.