The maximal width of the base of support (BSW): Clinical applicability and reliability of a preferred-standing test for measuring the risk of falling

The aim of this study was to test the reliability and validity of a preferred-standing test for measuring the risk of falling. The preferred-standing position of elderly fallers and non-fallers and healthy young adults was measured. The maximal BSW was measured. The absolute and relative reliability and discriminant validity were assessed. The expanded timed get-up-and-go test (ETGUG), one-leg stance test (OS), tandem stance (TS), and falls efficacy scale international version (FES-I) were used to determine criterion validity. In total, 146 persons (102 females, 44 males; mean age 55 ± 22 years, range 20-94) were recruited. Forty elderly community dwellers (8 fallers) and 26 young adults were tested twice to determine the test-retest reliability. The BSW showed acceptable test-retest reliability (Intraclass correlation coefficient, ICC2,1 = 0.77-0.83) and inter-rater reliability (ICC3,1 = 0.77-0.95) for all groups. The standard error of measurement (SEM) was between 0.77 and 1.87, and the smallest detectable change (SDC) was between 2.14 cm and 5.19 cm. The Bland-Altman plot revealed no systematic errors. There was significant difference between elderly fallers and non-fallers (F(1/75) = 11.951; p = 0.001. Spearman's rho coefficient values showed no correlation between the BSW and the ETGUG (−0.17, p = 0.47), OLS (−0.04, p = 0.65), TS (−0.11, p = 0.21), and FES-I (−0.10; p = 0.27). Only the BSW was a significant predictor for falling (odds ratio = 0.736, p = 0.007). The reliability and validity of the BSW protocol were acceptable overall. Prospective studies are warranted to evaluate the predictive value of the BSW for determining the risk of falling.