Assessing Plantar Sensation in the Foot Using the Foot Roughness Discrimination Test (FoRDT): A Reliability and Validity Study in Stroke

Abstract

Background The plantar foot 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 intrarater reliability, convergent and discriminant validity of the FoRDT. Design Test‐retest design. Setting Hospital outpatient. Participants Thirty‐two people with stroke (mean age 70 years) at least 3 months after stroke, and 32 healthy, age‐matched controls (mean age 70). Main Outcome Measures Roughness discrimination thresholds were quantified utilizing acrylic foot plates, laser cut to produce graded spatial gratings. Stroke participants were tested on three occasions, and by two different raters. Inter‐ and intrarater 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 interrater reliability and agreement were excellent (ICC =0.86 [95% CI 0.72‐0.92] and 0.90 [95% CI 0.76‐0.96]). 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 with nonfallers (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 characteristic 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) whereas 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 older population. It offers clinicians and researchers a sensitive and robust sensory measure and may further support the evaluation of rehabilitation targeting foot sensation. Level of Evidence III.

Lower Limb Somatosensory Discrimination Is Impaired in People With Parkinson's Disease: Novel Assessment and Associations With Balance, Gait, and Falls

“…The FoRDT, described and evaluated previously, assesses the haptic tactile sensory ability of the plantar aspect of the foot. It comprises a series of textured foot plates, each with standardized and quantifiable gratings.…”

“…In response to the perceived shortcomings of the existing clinical measures, we developed the following 3 novel and functionally oriented tests of somatosensory discrimination: the Foot Roughness Discrimination Test (FoRDT), the Step Height Discrimination Test (StepDT), and the Gradient Discrimination Test (GradDT). These functionally oriented tests have been described and evaluated previously in a stroke population, showing superior psychometric properties to the clinically feasible and psychometrically robust sensory measure, the EmNSA . To date, however, our novel tests have not been evaluated in people with PD.…”