Letter to the Editor: On 'Validity and reliability of the Nintendo Wii Balance Board for assessment of standing balance' by R.A. Clark et al. [Gait & Posture 31 (2010) 307-310]: are the conclusions stated by the authors justified?

摘要

The work by Clark and colleagues has generated great interest not only in the scientific community, but also on the Internet [1] and the general media. However, upon close examination of the methods and results presented in the original article, we believe that the conclusions the authors made are somewhat misleading and unsupported.First, there is the issue of how to establish when two methods or devices are equivalent and interchangeable. Lee and colleagues [2] offered some guidance suggesting that "two methods can be judged interchangeable provided all of the following conditions are met: first, the methods must not exhibit marked additive or non-additive systematic bias; second, the difference between the two mean readings is not "statistically significant"; third, the lower limit of the 95% confidence interval of the intraclass correlation is at least 0.75." The results presented by Clark et al. meet none of these criteria: there is an important systematic bias between the force platform (FP) and the Nintendo Wii Balance Board (WBB); the difference between the mean readings from the two devices is "statistically significant" (0 is never included in the confidence interval); the lower limit of the 95% confidence interval of the Intraclass Correlation Coefficient (ICC) between the measurements from the two devices is never above 0.71 and does not reach the 0.75 level suggested by Lee et al.; the Standard Error of the Measurement (SEM) of the WBB is always higher than that of the FP (up to 82% higher); and the Minimum Detectable Change MDC for the WBB is generally higher than that of the FP (as much as 92% higher, i.e., almost twice). Given these results, it is hard to understand how Clark and colleagues could state that "In this respect, we have shown that the WBB exhibits excellent test-retest reliability for COP path length assessment and possesses concurrent validity with a laboratory-grade FP." and that "In conclusion, the WBB provides comparable data to a FP when assessing COP path length during standing balance trials."