The development of an accelerometer-based measure of human upright static anterior-posterior postural sway under various sensory conditions: Test–retest reliability, scoring and preliminary validity of the Balance Accelerometry Measure (BAM)
Affiliations: [a] Department of Physical Therapy, Duquesne University, Pittsburgh, PA, USA | [b] Department of Otolaryngology, University of Pittsburgh, Pittsburgh, PA, USA | [c] Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA | [d] Department of Physical Therapy, University of Pittsburgh, Pittsburgh, PA, USA | [e] Crossroads Consulting LLC, Pittsburgh, PA, USA | [f] School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, PA, USA
Correspondence:
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Corresponding author: Gregory F. Marchetti, 600 Forbes Avenue, Pittsburgh, PA 15282, USA. Tel.: +1 412 396 5544; Fax: +1 412 396 4399; E-mail: Marchetti@duq.edu
Abstract: Background:Accelerometers are being used to assess postural control in adults, but there is little to support their reliability and validity. Objective:To estimate the test-retest reliability of the balance accelerometry measure (BAM) and to describe the known-groups validity of the BAM composite score. Methods:Two measures of standing postural sway were taken across six sensory (vision/stance surface) and motor stance (feet together or tandem) positions from eighteen patients with vestibular disorders and 84 healthy subjects. Test-retest reliability for postural sway was estimated across all conditions using intraclass correlation coefficient (ICC). A composite measure of sway standardized to young healthy subjects on eyes open firm surface stance was compared between groups. Results:Test-retest reliability of postural sway was good (ICC ⩾ 0.74) under all sensory conditions except eyes closed/tandem stance, which was slight to poor. Analysis of the receiver operating characteristic curve for composite scores indicated significant accuracy at identification of subjects in the vestibular/balance disorder groups. Composite standard scores equal or greater than 21.1 identified subjects with vestibular disorders with an accuracy of 72% sensitivity and 68% specificity. Conclusion:The BAM displays good-excellent reliability for five of six sensory-motor conditions. The composite score appears to differentiate healthy from subjects with vestibular disorders.
