Developing linear ADL ability measures based on the ADL Taxonomy: A Rasch analysis

Abstract

Purpose. The aim of this pilot study was to explore the possibility of developing linear measures of ADL ability based on the ADL Taxonomy and a three-category rating scale. Method. Data were obtained from medical records of adults with moderate to severe brain injury. The participants were rated on the ADL taxonomy, and recorded on the ADL Taxonomy Circle, based on direct observations. By applying the Rasch rating scale model, we examined the possibility of converting the raw ordinal scores into equal-interval estimates of the participants’ ADL ability. Results. The data analysis indicated that the rating scale used in this study displays sound psychometric properties. Items from the ADL taxonomy defined one construct after 10 actions were removed, but retention of all items did not disrupt the measurement system. Except for one item in each of five different activity domains, the item difficulty hierarchy was the same as in the hierarchy originally published, supporting reliability of the item difficulty estimates. The ADL taxonomy discriminated well between different levels of ability in this sample of persons with brain injury. Conclusion. This preliminary study indicates that the ADL taxonomy has potential to become a linear measure of a person's ability to perform ADL tasks.