Examining the reliability, correlation, and validity of commonly used assessment tools to measure balance

The Biodex SD Stability System has been shown to be a reliable assessment tool for postural stability. However, its ability to provide an accurate representation of balance has not been compared with functional performance measures such as the four-square step test (FSST) and timed-up-and-go test (TUG). The purpose of this study was to investigate reliability, internal consistency, and construct validity of FSST, TUG, and Biodex SD (limits of stability [LOS] and modified Clinical Test of Sensory Organization and Balance [m-CTSIB]).

An observational reliability and validity study was conducted. A convenience sample of 105 healthy adults, 77 females and 28 males, mean age 24.5 years old (± 4.66 SD) performed balance assessments including the FSST, TUG, Biodex SD LOS, and m-CTSIB. For LOS, the overall percentage and test duration were recorded. For m-CTSIB, the overall Sway Index was recorded. Condition 1 of the m-CTSIB represented simple postural stability.

The Biodex SD LOS overall percentage, TUG, and FSST showed strong to excellent test-retest reliability (ICC [3, 1] = .83 [mean 1: 58.14, mean 2: 60.54], .88 [mean 1: 6.98 seconds, mean 2: 6.91 seconds], .92 [mean 1: 6.29 seconds, mean 2: 6.14 seconds], respectively), while the Biodex SD m-CTSIB overall percentage demonstrated strong test-retest reliability (ICC [3, 1] = .75 [mean 1: 1.18, mean 2: 1.18]). The LOS test duration showed moderate test-retest reliability (ICC [3, 1] = .58 [mean 1: 38.55 seconds, mean 2: 37.10 seconds]), while the m-CTSIB condition 1 showed poor test-retest reliability (ICC [3, 1] = .24 [mean 1: 0.63, mean 2: 0.66]). Weak construct validity was found between TUG, FSST, and Biodex SD measures of LOS and m-CTSIB (r values = -0.15-0.22).

It is suggested that clinicians use more than one measure to assess different aspects of a patient's balance deficits to better guide treatment and intervention.