Clinimetric Properties of the de Morton Mobility Index in Healthy, Community-Dwelling Older Adults

Davenport SJ, de Morton NA. Clinimetric properties of the de Morton Mobility Index in healthy, community-dwelling older adults. Arch Phys Med Rehabil 2011; 92:51-8. Objective: To investigate the clinimetric properties of the de Morton Mobility Index (DEMMI) in healthy, community-dwelling older adults. Design: Cohort study. Setting: Retirement village and Returned and Services League (RSL) club in Melbourne, Australia. Participants: All participants were 65 years or older, healthy, and living within the community. The validation study included participants recruited from a retirement village (n=61), and the reliability studies included participants recruited from an RSL club and a subset of participants from the retirement village. Interventions: Not applicable. Main Outcome Measures: Mobility was assessed using the DEMMI. The percentage of participants who scored the highest and lowest possible score on the DEMMI was calculated to determine whether a floor or ceiling effect occurred. The minimal clinically important difference (MCID) was estimated using a distribution-based method. Reliability was assessed independently and concurrently using the minimal detectable change at 90% confidence (MDC90). Results: Evidence of convergent and discriminant validity was obtained for the DEMMI by examining correlations with measures of related constructs, the Lower Extremity Functional Scale (r=.69) and Quality of Life Scale scores (r=.28), respectively. Participants who ambulated without a gait aid (82.62 +/- 10.63) had significantly higher (P<.0) DEMMI scores than those who ambulated with an aid (64.1 +/- 12.40), providing evidence of known groups validity. No floor or ceiling effect was identified. The MCID was 7 points. The MDC90 was 13 (95% CI, 8.76-17.05) points on the 100-point scale. Conclusion: DEMMI scores in healthy, community-dwelling older adults are both valid and reliable.