Validity and Reliability of Limits-of-Stability Testing: A Comparison of 2 Postural Stability Evaluation Devices

Abstract

A lack of published comparisons between measures from commercially available computerized posturography devices and the outcome measures used to define the limits of stability (LOS) makes meaningful interpretation of dynamic postural stability measures difficult. To compare postural stability measures between and within devices to establish concurrent and construct validity and to determine test-retest reliability for LOS measures generated by the NeuroCom Smart Balance Master and the Biodex Balance System. Cross-sectional study. Controlled research laboratory. A total of 23 healthy participants with no vestibular or visual disabilities or lower limb impairments. The LOS were assessed during 2 laboratory test sessions 1 week apart. Three NeuroCom LOS variables (directional control, endpoint excursion, and movement velocity) and 2 Biodex LOS variables (directional control, test duration). Test-retest reliability ranged from high to low across the 5 LOS measures (intraclass correlation coefficient [2,k] = 0.82 to 0.48). Pearson correlations revealed 4 significant relationships (P < .05) between and within the 2 computerized posturography devices (r = 0.42 to -0.65). Based on the wide range of intraclass correlation values we observed for the NeuroCom measures, clinicians and researchers alike should establish the reliability of LOS testing for their own clinics and laboratories. The low to moderate reliability outcomes observed for the Biodex measures were not of sufficient magnitude for us to recommend using the LOS measures from this system as the gold standard. The moderate Pearson interclass correlations we observed suggest that the Biodex and NeuroCom postural stability systems provided unique information. In this study of healthy participants, the concurrent and construct validity of the Biodex and NeuroCom LOS tests were not definitively established. We recommend that this study be repeated with a clinical population to further explore the matter.