Title

Clinimetric evaluation of the physical mobility scale supports clinicians and researchers in residential aged care

Date of this Version

11-1-2008

Document Type

Journal Article

Publication Details

Interim status: Citation only.

Barker, A. L., Nitz, J. C., Low Choy, N. L., & Haines, T. P. (2008). Clinimetric evaluation of the physical mobility scale supports clinicians and researchers in residential aged care. Archives of physical medicine and rehabilitation, 89(11), 2140-2145.

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2008 HERDC submission. FoR Code: 1117

© Copyright by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation, 2008

Abstract

Objective
To investigate the interrater agreement and the internal construct validity of the Physical Mobility Scale, a tool routinely used to assess mobility of people living in residential aged care.

Design
Prospective, multicenter, external validation study.

Setting
Nine residential aged care facilities in Australia.

Participants
Residents (N=186). Phase 1 cohort (99 residents; mean age, 85.22±5.1y); phase 2 cohort (87 residents; mean age, 81.59±10.69y).

Interventions
Not applicable.

Main Outcome Measures
Kappa statistics, minimal detectable change (MDC90) scores, and Bland-Altman plots were used to assess interrater agreement. Scale unidimensionality, item hierarchy, and person separation were examined with Rasch analysis for both cohorts.

Results
Agreement between raters on 6 of the 9 Physical Mobility Scale items was high (κ>.60). The MDC90 value was 4.39 points, and no systematic differences in scores between raters were found. The Physical Mobility Scale showed a unidimensional structure demonstrated by fit to the Rasch model in both cohorts (phase 1: χ2=23.90, P=.16, person separation index=0.96; phase 2: χ2=22.00, P=.23, person separation index=0.96). Standing balance was the most difficult item in both cohorts (phase 1: logit=2.48, SE, 0.16; phase 2: logit=2.53, SE, 0.15). The person-item threshold map indicated no floor or ceiling effects in either cohort.

Conclusions
The Physical Mobility Scale demonstrated good interrater agreement and internal construct validity with good fit to the Rasch model in both cohorts. The comparative results across the 2 cohorts indicate generality of the findings. The Physical Mobility Scale total raw scores can be converted to Rasch transformed scores, providing an interval measure of mobility. The Physical Mobility Scale may be suited to a range of clinical and research applications in residential aged care.

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This document has been peer reviewed.