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 2.14cm and 5.19cm. 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.