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.

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.