Interrater Reliability of the 6-Minute Walk Test in Women With Hip Fracture

Abstract

Background and purpose: The 6-minute walk test (6MWT) is widely used as a clinical outcome measure. However, the reliability of the 6MWT is unknown in individuals who have recently experienced a hip fracture. The aim of this study was to evaluate the relative and absolute interrater reliability of the 6MWT in individuals with hip fracture.

Methods: Two senior physical therapy students independently examined a convenience sample of 20 participants in a randomized order. Their assessments were separated by 2 days and followed the guidelines of the American Thoracic Society. Hip fracture-related pain was assessed with the Verbal Ranking Scale.

Results: Participants (all women) with a mean (standard deviation) age of 78.1 (5.9) years performed the test at a mean of 31.5 (5.8) days postsurgery. Of the participants, 10 had a cervical fracture and 10 had a trochanteric fracture. Excellent interrater reliability (intraclass correlation coefficient [ICC2.1] = 0.92; 95% confidence interval, 0.81-0.97) was found, and the standard error of measurement and smallest real difference were calculated to be 21.4 and 59.4 m, respectively. Bland-Altman plots revealed no significant difference (mean of 3.2 [31.5] m, P = .83) between the 2 raters, and no heteroscedasticity was observed (r = -0.196, P = .41). By contrast, participants walked an average of 21.7 (22.5) m longer during the second trial (P = .002). Participants with moderate hip fracture-related pain walked a shorter distance than those with no or light pain during the first test (P = .04), but this was not the case during the second test (P = .25).

Conclusion: The interrater reliability of the 6MWT is excellent, and changes of more than 21.4 m (group level) and 59.4 m (individual participants with hip fracture) indicate a real change in the 6MWT. Measuring hip fracture-related pain during testing is recommended for individuals with hip fracture who undergo the 6MWT.