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)

Abstract

Accelerometers are being used to assess postural control in adults, but there is little to support their reliability and validity. To estimate the test-retest reliability of the balance accelerometry measure (BAM) and to describe the known-groups validity of the BAM composite score. 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. 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. 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.