• Excellent cross-cultural validity, intra-test reliability and construct validity of the Dutch Rivermead Mobility Index in patients after stroke undergoing rehabilitation

      Roorda, L.D.; Green, J.R.; De Kluis, K.R.; Molenaar, I.W.; Bagley, Pamela J.; Smith, J.; Geurts, A.C. (2008)
      OBJECTIVE: To investigate the cross-cultural validity of international Dutch-English comparisons when using the Dutch Rivermead Mobility Index (RMI), and the intra-test reliability and construct validity of the Dutch RMI. METHODS: Cross-cultural validity was studied in a combined data-set of Dutch and English patients undergoing rehabilitation after stroke, who were assessed with the Dutch version of the RMI and the original English RMI, respectively. Mokken scale analysis was used to investigate unidimensionality, monotone homogeneity model fit, and differential item functioning between the Dutch and the English RMI. Intra-test reliability and construct validity were studied in the Dutch patients by calculating the reliability coefficient and correlating the Dutch RMI and the Dutch Barthel Index. RESULTS: The RMI was completed for Dutch (n = 200) and English (n = 420) patients after stroke. The unidimensionality and monotone homogeneity model fit of the RMI were excellent: combined Dutch-English data-set (coefficient H = 0.91); Dutch data-set (coefficient H = 0.93); English data-set (coefficient H = 0.89). No differential item functioning was found between the Dutch and the English RMI. The intra-test reliability of the Dutch RMI was excellent (coefficient rho = 0.97). In a sub-sample of patients (n = 91), the Dutch RMI correlated strongly with the Dutch Barthel Index (Spearman's correlation coefficient rho = 0.84). CONCLUSION: The Dutch RMI allows valid international Dutch-English comparisons, and has excellent intra-test reliability and construct validity.
    • Excellent cross-cultural validity, intra-test reliability and construct validity of the Dutch Rivermead Mobility Index in patients after stroke undergoing rehabilitation

      Roorda, L.D.; Green, J.R.; De Kluis, K.R.; Molenaar, I.W.; Bagley, Pamela J.; Smith, J.; Geurts, A.C. (2008)
      OBJECTIVE: To investigate the cross-cultural validity of international Dutch-English comparisons when using the Dutch Rivermead Mobility Index (RMI), and the intra-test reliability and construct validity of the Dutch RMI. METHODS: Cross-cultural validity was studied in a combined data-set of Dutch and English patients undergoing rehabilitation after stroke, who were assessed with the Dutch version of the RMI and the original English RMI, respectively. Mokken scale analysis was used to investigate unidimensionality, monotone homogeneity model fit, and differential item functioning between the Dutch and the English RMI. Intra-test reliability and construct validity were studied in the Dutch patients by calculating the reliability coefficient and correlating the Dutch RMI and the Dutch Barthel Index. RESULTS: The RMI was completed for Dutch (n = 200) and English (n = 420) patients after stroke. The unidimensionality and monotone homogeneity model fit of the RMI were excellent: combined Dutch-English data-set (coefficient H = 0.91); Dutch data-set (coefficient H = 0.93); English data-set (coefficient H = 0.89). No differential item functioning was found between the Dutch and the English RMI. The intra-test reliability of the Dutch RMI was excellent (coefficient rho = 0.97). In a sub-sample of patients (n = 91), the Dutch RMI correlated strongly with the Dutch Barthel Index (Spearman's correlation coefficient rho = 0.84). CONCLUSION: The Dutch RMI allows valid international Dutch-English comparisons, and has excellent intra-test reliability and construct validity.
    • Item hierarchy-based analysis of the Rivermead Mobility Index resulted in improved interpretation and enabled faster scoring in patients undergoing rehabilitation after stroke

      Roorda, L.D.; Green, J.R.; Houwink, A.; Bagley, Pamela J.; Smith, J.; Molenaar, I.W.; Geurts, A.C. (2012)
      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.
    • The Rivermead Mobility Index allows valid comparisons between subgroups of patients undergoing rehabilitation after stroke who differ with respect to age, sex, or side of lesion

      Roorda, L.D.; Green, J.R.; Houwink, A.; Bagley, Pamela J.; Smith, J.; Molenaar, I.W.; Geurts, A.C. (2012)
      OBJECTIVE: To investigate differential item functioning or item bias of the Rivermead Mobility Index (RMI) and its impact on the drawing of valid comparisons with the RMI between subgroups of patients after stroke who differ with respect to age, sex, or side of lesion. DESIGN: Cross-sectional study. SETTING: A rehabilitation center in the Netherlands and 2 stroke rehabilitation units and the wider community in the United Kingdom. PARTICIPANTS: The RMI was completed for patients undergoing rehabilitation after stroke (N=620; mean age +/- SD, 69.2+/-12.5y; 297 [48%] men; 269 [43%] right hemisphere lesion, and 304 [49%] left hemisphere lesion). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Mokken scale analysis was used to investigate differential item functioning of the RMI between subgroups of patients who differed with respect to age (young vs older), sex (men vs women), and side of stroke lesion (right vs left hemisphere). RESULTS: No differential item functioning was found for any of the comparison subgroups. CONCLUSIONS: The RMI allows valid comparisons to be made between subgroups of patients undergoing rehabilitation after stroke who differ with respect to age, sex, or side of lesion.