Reliability, validity and minimal detectable change of 2-minute walk test, 6-minute walk test and 10-meter walk test in frail older adults with dementia

Abstract

Background: Walk tests are commonly used to evaluate walking ability in frail older adults with dementia but their psychometric evidence in this population is lacking.

Objectives: 1) To examine test-retest and inter-rater reliability, construct and known-group validity, and minimal detectable change at 95% level of confidence (MDC₉₅) of walk tests in frail older adults with dementia, and 2) to examine the feasibility and consistency of a cueing system in facilitating participants in completing walk tests.

Design: Psychometric study with repeated measures.

Setting: Day care and residential care facilities.

Participants: Thirty-nine frail older adults with a mean age 87.1 and a diagnosis of dementia or Alzheimer's disease who were able to walk independently for at least 15 m.

Methods: The participants underwent a 2-minute walk test (2MWT), 6-minute walk test (6MWT) and 10-meter walk test (10MeWT) on 6 separate occasions under 2 independent assessors using a cueing system. Functional status was measured using the Elderly Mobility Scale (EMS), Berg Balance Scale (BBS) and Modified Barthel Index (MBI).

Results: Excellent test-retest (ICC = 0.91-0.98) and inter-rater reliability (ICC = 0.86-0.96) were shown in the 2MWT, 6MWT and 10MeWT. The walk tests were strongly correlated with each other (ρ = 0.85-0.94). The correlations between the walk tests and the functional measures were moderate in general (ρ = 0.34-0.55). All the walk tests were able to distinguish between those who could walk outdoor and indoor only (p ≤ .036). The MDC₉₅ were 9.1 m in the 2MWT, 28.1 m in the 6MWT, and.16 m/s in the 10MeWT. The cues provided by the assessors in the walk tests were generally consistent (ICC = 0.62-0.89).

Conclusions: The 2MWT, 6MWT and 10MeWT are reliable and valid measures in evaluating walking ability in frail older adults with dementia. The MDC₉₅ of the walk tests has been established. The cueing system is feasible and reliable to facilitate the administration of the walk tests in this population group.

Keywords: Dementia; Mobility; Physical assessment; Psychometrics; Walking.