Validation of the Narrowing Beam Walking Test in lower limb prosthesis users

Publication date: Available online 11 April 2018
Source:Archives of Physical Medicine and Rehabilitation
Author(s): Andrew Sawers, Brian Hafner
ObjectiveTo evaluate the content, construct, and discriminant validity of the Narrowing Beam Walking Test (NBWT), a performance-based balance test for lower limb prosthesis users.DesignCross-sectional study.SettingResearch laboratory and prosthetics clinic.ParticipantsForty unilateral transtibial and transfemoral prosthesis users.InterventionNot applicable.Main Outcome Measure(s)Content validity was examined by quantifying the percentage of participants receiving maximum or minimum scores (i.e. ceiling and floor effects). Convergent construct validity was examined using correlations between participants' NBWT scores and scores or times on existing clinical balance tests regularly administered to lower limb prosthesis users. Known-groups construct validity was examined by comparing NBWT scores between groups of participants with different fall histories, amputation levels, amputation etiologies, and functional levels. Discriminant validity was evaluated by analyzing the area under each test's Receiver Operating Characteristic (ROC) curve.ResultsNo minimum or maximum scores were recorded on the NBWT. NBWT scores demonstrated strong correlations (|rs|=.70‒.85) with scores/times on performance-based balance tests (Timed up and Go, Four Square Step Test, and Berg Balance Scale), and a moderate correlation (|rs|=.49) with the self-report Activities-specific Balance Confidence scale. NBWT performance was significantly lower among participants with a history of falls (p=.003), transfemoral amputation (p=.011), and a lower mobility level (p<.001). The NBWT also had the largest area under the ROC curve (.81), and was the only test to exhibit an area that was statistically significantly greater than 0.50 (i.e. chance).ConclusionThe results provide strong evidence of content, construct, and discriminant validity for the NBWT as a performance-based test of balance ability. The evidence supports its use to assess balance impairments and fall risk in unilateral transtibial and transfemoral prosthesis users.



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