Validation of the stabilometer balance test: Bridging the gap between clinical and research based balance control assessments for stroke patients

Abstract

Background: A pronounced discrepancy exists between balance assessments for stroke survivors that are used for clinical purposes and those used for research. Clinical assessments like the Berg Balance Scale generally have stronger ecological validity, whereas research-based assessments like posturography are generally more reliable and precise. We developed a stabilometer balance test (SBT) that aims to couple measurement reliability and precision to clinical meaningfulness by means of a personalized and adaptive test procedure. Research question: To examine the validity, reliability, and measurement error of the stabilometer balance test in inpatient stroke patients. Methods: In this cross-sectional study, inpatient stroke patients (FAC > 2) were tested on a stabilometer with adjustable resistance to mediolateral movement. A modified staircase procedure was used to adapt task difficulty (i.e., rotational stiffness) on a trial-by-trial basis. The main outcome was the threshold stiffness at which a patient could just stay balanced. Threshold stiffness was correlated with the Berg Balance Scale and posturography measurements to determine concurrent validity (N = 86). Test-retest reliability (N = 23) was analyzed with the Intraclass Correlation Coefficient (ICC). Floor and ceiling effects were assessed. The minimal detectable change was determined at individual and group level. Results: Threshold rotational stiffness moderately correlated with the Berg Balance Scale (r=−0.559, p < 0.001), and the absolute path length of the center of pressure during posturography (r=0.348, p = 0.006). Test-retest reliability was good to excellent (ICC=0.869; 95%CI=0.696-0.944). There were no floor or ceiling effects. The minimal detectable change was sufficiently small to detect relevant changes in balance control both on individual and group level. Relevance: The SBT is both a valid and reliable balance assessment in stroke patients. It is at least as precise as current clinically preferred measures and does not suffer from ceiling effects. Therefore, it is suitable for use in clinical practice as well as research.

The Effect of External Attentional Focus and Self-Controlled Feedback on Motor Learning in Older Adults

“…In the present study, learning and motor performance were reported as the amount of time needed to maintain dynamic balance in the elderly. The stabilometer was used to measure dynamic balance [21]. This device includes a moving plate (platform), a chassis and a control unit.…”

Are the effects of internal focus instructions different from external focus instructions given during balance training in stroke patients? A double-blind randomized controlled trial

“…A custom-made, validated balance board task 32 was used to test patients' balance performance, and also for the interventions ( Figure S1). This balance board task taxes mediolateral balance control, which is often impaired after stroke.…”

“…With this procedure, task difficulty is adjusted on a trial-to-trial basis, based on prespecified criteria. Please see Brouwer et al 32 for the full-test protocol. Patients only received unfocused instructions ("stand as still as possible").…”

“…The rotational stiffness assessment has excellent test-retest reliability (intraclass correlation coefficient (ICC) = 0.87) and construct validity (r = -0.56 with Berg Balance Scale), and a minimum detectable change of 3.20 Nm/rad on group level. 32 Next, we measured patients' sway at their baseline threshold stiffness in single-(as performance measure) and dual-task conditions (as automaticity measure). Sway was defined as the root-mean-square error deviation around the board's average position (degrees).…”

“…The balance board's potentiometer data were filtered with a bidirectional, lowpass (8 Hz) Butterworth filter. We used non-linear regression to determine the patients' individual threshold stiffness (see Brouwer et al 32…”