Rasch analysis of the ADL scale of the A-ONE.

The ADL-focused Occupation-based Neurobehavioral Evaluation (A-ONE; Arnadóttir, 1990) can be used to evaluate both performance of activities of daily living (ADL) tasks and neurobehavioral problems that interfere with ADL task performance among clients with neurological disorders. This study examined the rating scale structure and aspects of validity and reliability of the A-ONE's ordinal ADL scale by applying Rasch analysis methods (Bond & Fox, 2001). Rasch analysis of 209 clients' A-ONE assessments indicated that misfit of items to the ADL scale could be reduced by removing the two communication items. Threshold disordering could be corrected by combining two adjacent scoring categories (supervision and verbal assistance), thus supporting four response categories. Separation reliability for item calibrations (.98) was high and acceptable for people (.90). Finally, principal components analysis of the residuals supported unidimensionality. The study provided support for converting the ordinal ADL scale to an interval scale that has potential to be used to measure changes in ADL task performance over time.