Item Hierarchy–Based Analysis of the Rivermead Mobility Index Resulted in Improved Interpretation and Enabled Faster Scoring in Patients Undergoing Rehabilitation After Stroke

Abstract Roorda LD, Green JR, Houwink A, Bagley PJ, Smith J, Molenaar IW, Geurts AC. Item hierarchy – based analysis of the Rivermead Mobility Index resulted in improved interpretation and enabled faster scoring in patients undergoing rehabilitation after stroke. Objective To enable improved interpretation of the total score and faster scoring of the Rivermead Mobility Index (RMI) by studying item ordering or hierarchy and formulating start-and-stop rules in patients after stroke. Design Cohort study. Setting Rehabilitation center in the Netherlands; stroke rehabilitation units and the community in the United Kingdom. Participants Item hierarchy of the RMI was studied in an initial group of patients (n=620; mean age ± SD, 69.2±12.5y; 297 [48%] men; 304 [49%] left hemisphere lesion, and 269 [43%] right hemisphere lesion), and the adequacy of the item hierarchy – based start-and-stop rules was checked in a second group of patients (n=237; mean age ± SD, 60.0±11.3y; 139 [59%] men; 103 [44%] left hemisphere lesion, and 93 [39%] right hemisphere lesion) undergoing rehabilitation after stroke. Interventions Not applicable. Main Outcome Measures Mokken scale analysis was used to investigate the fit of the double monotonicity model, indicating hierarchical item ordering. The percentages of patients with a difference between the RMI total score and the scores based on the start-and-stop rules were calculated to check the adequacy of these rules. Results The RMI had good fit of the double monotonicity model (coefficient H T =.87). The interpretation of the total score improved. Item hierarchy – based start-and-stop rules were formulated. The percentages of patients with a difference between the RMI total score and the score based on the recommended start-and-stop rules were 3% and 5%, respectively. Ten of the original 15 items had to be scored after applying the start-and-stop rules. Conclusions Item hierarchy was established, enabling improved interpretation and faster scoring of the RMI.