Linking the Activity Measure for Post Acute Care and the Quality of Life Outcomes in Neurological Disorders

Abstract

Haley SM, Ni P, Lai J-S, Tian F, Coster WJ, Jette AM, Straub D, Cella D. Linking the Activity Measure for Post Acute Care and the Quality of Life Outcomes in Neurological Disorders. Objective To use item response theory (IRT) methods to link physical functioning items in the Activity Measure for Post Acute Care (AM-PAC) and the Quality of Life Outcomes in Neurological Disorders (Neuro-QOL). Design Secondary data analysis of the physical functioning items of AM-PAC and Neuro-QOL. We used a nonequivalent group design with 36 core items common to both instruments and a test characteristic curve transformation method for linking AM-PAC and Neuro-QOL scores. Linking was conducted so that both raw and scaled AM-PAC and Neuro-QOL scores (mean ± SD converted-logit scores, 50±10) could be compared. Setting AM-PAC items were administered to rehabilitation patients in post–acute care (PAC) settings. Neuro-QOL items were administered to a community sample of adults through the Internet. Participants PAC patients (N=1041) for the AM-PAC sample and community-dwelling adults (N=549) for the Neuro-QOL sample. Interventions Not applicable. Main Outcome Measures Mobility (N=25) and activity of daily living (ADL) items (N=11) common to both instruments were included in analysis. Results Neuro-QOL items were linked to the AM-PAC scale by using the generalized partial credit model. Mobility and ADL subscale scores from the 2 instruments were calibrated to the AM-PAC metric. Conclusions An IRT-based linking method placed AM-PAC and Neuro-QOL mobility and ADL scores on a common metric. This linking allowed estimation of AM-PAC mobility and ADL subscale scores based on Neuro-QOL mobility and ADL subscale scores and vice versa. The accuracy of these results should be validated in a future sample in which participants respond to both instruments.