The scale for retropulsion: Internal consistency, reliability and construct validity

Abstract

Background: Retropulsion is an impairment of body orientation against gravity in the sagittal plane. In a Delphi study, the Scale for Retropulsion (SRP) was developed with a high level of expert agreement.

Objective: To assess the clinimetric properties of the German SRP in patients with neurological disorders.

Methods: The SRP was applied to 70 hospitalized patients with neurological disorders (stroke, critical illness neuropathy and/or myopathy, Parkinson syndromes). Internal consistency was determined with the Cronbach ɑ. Test-retest and interrater reliabilities were evaluated with the weighted kappa, intraclass correlation coefficient (ICC), and Bland-Altman plots. The construct validity was evaluated with Spearman correlation.

Results: The median (interquartile range) SRP score was 5 (3-8) and ranged from 0 to 22 (total scale range: 0 to 24). The SRP had excellent internal consistency (Cronbach ɑ=0.875) and good to excellent test-retest reliability (weighted kappa=0.957, ICC=0.957) and interrater reliability (weighted kappa=0.837, ICC=0.837). Analysis of construct validity resulted in good correlations with other clinical balance scales (r_Sp>0.80), and fair to moderate correlations with posturographic measures (r_Sp=0.27-0.56) and the subjective postural vertical error in the sagittal plane (r_Sp=-0.325, P=0.012) as well as the range in the frontal plane (r_Sp=0.359, P=0.007). The SRP discriminated between patients classified with and without retropulsion by an independent clinical expert (P<0.001).

Conclusion: The SRP provides a valid and reliable bedside test to quantify retropulsion in individuals with neurological disorders.

Keywords: Backward disequilibrium; Clinimetric properties; Neurological disorders; Reliability; Scale for Retropulsion; Validity.