Reliability of the two-minute walk test in individuals with transtibial amputation

Objective: To determine inter- and intrarater reliability of the two-minute walk test (2MWT) in individuals with transtibial amputation.

Design: Prospective; test-retest method by a pair of trained physical therapists.

Setting: Two regional amputee rehabilitation centers in Canada.

Participants: Thirty-three subjects (23 men, 10 women; mean age +/- standard error, 63.6+/-2.0y) with transtibial amputation; 6 in outpatient rehabilitation, 27 in inpatient rehabilitation. The most common primary diagnoses were peripheral vascular disease (n=15) and diabetes (n=11).

Interventions: Each subject performed a total of four 2MWTs, 1 test for each rater, on 2 consecutive days at approximately the same time of day. Subjects were given at least a 20-minute rest between tests. The order of raters was randomized on the first day and reversed for the next day. The walk tests were performed in the same enclosed corridors with the same starting point for all tests. The subjects were familiar with the test or were given 1 or more practice tests at least 1 day before testing. Subjects were allowed to walk with a mobility aid of their choice. Raters used a digital stopwatch to time the tests and a calibrated wheel with a counter to measure the distance walked in meters. The raters were blinded to each other's scores.

Main outcome measure: Distance walked in 2 minutes (in meters).

Results: Within-rater reliability was high (intraclass correlation coefficient [ICC],.90-.96). Between rater reliability was also high (ICC.98-.99). Analysis of variance (ANOVA) showed a significant effect for day of test (P<.001) in the inpatient group but no effect for therapist (P=.098) or for interaction of day and therapist (P=.710). Similarly, in the outpatient group, ANOVA showed a significant effect for day (P=.013) but no effect for therapist (P=.259) or interaction of day and therapist (P=.923).

Conclusion: Although the 2MWT showed evidence of inter- and intrarater reliability in individuals with unilateral below-knee amputation, the distance walked in 2 minutes continued to improve over time. This improvement was not solely the result of a training and learning effect.