The Development of a Comprehensive Physical Function Measure for the Intensive Care Unit Using Rasch Analysis and Item Response Theory

Abstract

Objective: This study serves to create a comprehensive, robust functional measurement tool for use with patients in the intensive care unit. Design: Two physical therapists conducted outcome measure research at a large hospital in the Northeast United States using item response theory (IRT) Rasch analysis for individual activity task evaluation, ranking of task difficulty, and removal of duplicate tasks. IRT Rasch analysis included item fit, hierarchy, reliability, dimensionality, differential item functioning (DIF), and probability. Results: Fifteen items out of a total of 53 met the requirements for an optimal rating scale. The items were ranked according to difficulty and there was no misfit. The reliability indexes were 5.13, α= 0.96, and 21.52, α= 1.00 for person and item scores respectively confirming scale hierarchy. The Cronbach α (KR-20) person raw score “test” reliability was 0.96, with standard error of measurement 2.72. DIF was deemed nonsignificant, and the probability curves were well delineated and ordered. Summary: A robust, reliable, and valid 15-item Comprehensive Physical Function Measure for use in the intensive care unit was developed through Rasch analysis and item response theory.