Reliability of the Six-minute Walk Test in Individuals with Transtibial Amputation

Objective

To determine inter- and intra-rater reliability of the Six-minute walk test (6MWT) in individuals with Transtibial Amputation.

Design

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

Setting

Indoor Physical Therapy department of the National Institute for the Orthopaedically Handicapped (NIOH), Kolkata.

Participants

Twenty one subjects (16 men, 5 women; mean age + mean standard error: 42.95 + 3.02 year) with transtibial amputation, who had completed two weeks of prosthetic training in the Inpatient Rehabilitation set up.

Interventions

Each subject performed a total of four 6MWTs, one test for each rater, on two consecutive days at approximately the same time of day. Subjects were given at least a 20 minutes rest between tests. The order of raters were 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. Subjects were allowed to walk with a mobility aid of their choice. Raters used a digital stopwatch to time the tests and the distance walked was measured in meters with the help of measuring tape. The raters were blinded to each other's scores.

Main Outcome Measure

Distance walked in 6 minutes (in meters).

Results

Within-rater reliability was good, with ICCs ranging from 0.79 to 0.83. Between-rater reliability was also high, with ICCs ranging from 0.81 to 0.88. A 2-way repeated-measures ANOVA showed significant differences (P<0.001) both within raters and between raters. It was seen that the proportion of variation within raters was more for the second rater whereas the proportion of variation between raters were more on the first day i.e day 1 of the test. Regardless of the tester, distances walked on day 2 were greater than on day1.

Conclusion

Although the 6 MWT showed good evidence of inter and intra rater reliability in individuals with unilateral below knee amputation, the distances walked in 6 minutes continued to improve over time. This improvement was mainly the result of training and learning effect.