Assessing plantar sensation in the foot using the FOot Roughness Discrimination Test (FoRDT™): a reliability and validity study in stroke.

Abstract

BACKGROUND: The foot sole represents a sensory dynamometric map and is essential for balance and gait control. Sensory impairments are common, yet often difficult to quantify in neurological conditions, particularly stroke. A functionally oriented and quantifiable assessment, the Foot Roughness Discrimination Test (FoRDT™), was developed to address these shortcomings. OBJECTIVE: To evaluate inter- and intra-rater reliability, convergent and discriminant validity of the Foot Roughness Discrimination Test (FoRDT™). DESIGN: Test-retest design. SETTING: Hospital Outpatient. PARTICIPANTS: Thirty-two people with stroke (mean age 70) at least 3 months after stroke, and 32 healthy, age-matched controls (mean age 70). MAIN OUTCOME MEASURES: Roughness discrimination thresholds were quantified utilising acrylic foot plates, laser-cut to produce graded spatial gratings. Stroke participants were tested on three occasions, and by two different raters. Inter- and intra-rater reliability and agreement were evaluated with Intraclass Correlation Coefficients and Bland-Altman plots. Convergent validity was evaluated through Spearman rank correlation coefficients (rho) between the FoRDT™ and the Erasmus modified Nottingham Sensory Assessment (EmNSA). RESULTS: Intra- and inter rater reliability and agreement were excellent (ICC =.86 (95% CI .72-.92) and .90 (95% CI .76 -.96)). Discriminant validity was demonstrated through significant differences in FoRDT™ between stroke and control participants (p< .001). Stroke fallers had statistically significant higher FoRDT™ scores compared to non-fallers (p=.01). Convergent validity was demonstrated through significant and strong correlations (rho) with the Erasmus MC Nottingham Sensory Assessment (r=.69, p<.01). Receiver Operator Curve analysis indicated the novel test to have excellent sensitivity and specificity in predicting the presence of self- reported sensory impairments. Functional Reach test significantly correlated with FoRDT™ (r=.62, p< .01) whilst measures of postural sway and gait speed did not (r=.16-.26, p>.05). CONCLUSIONS: This simple and functionally oriented test of plantar sensation is reliable, valid and clinically feasible for use in an ambulatory, chronic stroke and elderly population. It offers clinicians and researchers a sensitive and robust sensory measure and may further support the evaluation of rehabilitation targeting foot sensation. This article is protected by copyright. All rights reserved.