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

Abstract

Background:Walk tests are frequently used in evaluating frail older adults with multi-morbidities but their psychometric properties in this population are unclear. This study aimed at determining 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. Methods: In this cross-sectional psychometric study with repeated measures, a convenient sample of older adults who were frail and able to walk independently for at least 15 metres were recruited from day care and residential care facilities. All participants completed a 2-minute walk test (2MWT), 6-minute walk test (6MWT) and 10-metre walk test (10MeWT) on six separate occasions over a 2-week period under two independent examiners. Functional status was measured using the Elderly Mobility Scale (EMS), Berg Balance Scale (BBS) and Modified Barthel Index (MBI). Health-related quality of life was measured with the 12-Item Short Form Health Survey (SF-12). Result: Forty-four frail older adults were examined. Excellent test-rest (ICC=0.95-0.99) and inter-rater reliability (ICC=0.91-0.97) were shown in all the walk tests. Good to strong correlations were found between the walk tests and the EMS (r=0.53-0.57), BBS (r=0.59-0.66) and MBI (r=0.55-0.59). The correlations between the walk tests and the SF-12 were generally weak (r=0.05-0.30). All the walk tests were able to distinguish between those who used no walking aid and quadripod or walking frame (p≤0.004), and those who could walk outdoor and indoor only (p≤0.002). The MDC95 were 7.7m in the 2MWT, 24.7m in the 6MWT, and 0.13m/s in the 10MeWT. Discussion: The 2MWT, 6MWT and 10MeWT are reliable and valid measures in evaluating the walking performance of frail older adults. The MDC95 of the walk tests has been recommended for this population group.