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Test-Retest Reliability of the Sway Balance Mobile Application


AUTHORS: Ryan Z. Amick, PhD, Alex Chaparro, PhD, Jeremy A. Patterson, PhD, Michael J. Jorgensen, PhD

BACKGROUND: The SWAY Balance Mobile Application is an FDA-cleared balance testing system which uses the built-in tri-axial accelerometers of a mobile electronic device to objectively assess postural movement. The system was designed to provide a means of quantitative balance assessment in clinical and on-field environments. The purpose of this study was to determine the intrasession and intersession reliability, as well as the minimum difference to be considered real, of the SWAY Balance Mobile Application.

METHODS: 24 individuals (15 male, 9 female; aged 25.96 (95.78 years)) performed the SWAY Balance protocol twice per testing session over a period of three testing sessions. Each testing session was separated by a minimum of seven days. Interclass Correlation Coefficients were calculated as an indication of the test-retest reliability. The minimum difference to be considered real was calculated to determine the minimum score change necessary to indicate an actual change in balance performance.

RESULTS: Mean SWAY Balance scores ranged from 86.90 (914.37) to 89.90 (911.19). Repeated measures ANOVA revealed no significant mean differences between SWAY balance scores of the experimental trials (F(5,115) 0.673; p 0.65). Excellent reliability was found (ICC(3,1) 0.76; SEM 5.39) with a minimum difference to be considered real of approximately 15.

CONCLUSION: Results indicate that SWAY provides excellent overall reliability. However, it may be appropriate to have subjects perform a familiarization trial at the beginning of each testing session. Additionally, SWAY may demonstrate a ceiling effect when assessing balance improvements in those who already demonstrate good balance.