Test–retest reliability and validity of normative cut-offs of the two devices measuring touch threshold: Weinstein Enhanced Sensory Test and Pressure-Specified Sensory Device

Abstract

Introduction Touch threshold screening instruments must accurately distinguish normal versus abnormal sensation to screen nerve pathology. This study was conducted to find out whether two touch threshold measuring devices (i.e. Weinstein Enhanced Sensory Test (WEST) and Pressure-Specified Sensory Device (PSSD) provide consistent results and indicators of “normal” sensation, and secondarily what rules best define normality. Methods The study design was a cross-sectional reliability and validity assessment with 23 healthy participants. Instruments were applied in random order on the pulp of the middle and little fingers of both hands; with five applications on each digit. Cut-offs of 3, 4, and 5 correct responses were used to classify the response as being normal. Weighted kappa and percent agreement were used to indicate test–retest reliability of the WEST, and validity was determined by calculating the percentage of normal controls that achieved a normal score. The Bland–Altman method was used to characterize the retest reliability of PSSD, and validity was determined by whether the mean of the score is different from the normative scores. Results The agreement between test and retest of WEST (detection level = 3/5) was almost perfect ( k = 1). The average percentages of normal detection of the WEST on two test/retest were 93% and 97% (detection level = 4/5) and 82% and 85% (detection level = 5/5). All mean PSSD tests values were found within the predetermined normal range. The Bland–Altman plot demonstrated a minimal mean difference between test occasions and similar limits of agreement across the four test locations. Discussion The study found that more than 90% of the tests with healthy young participants were reliable and valid in relation to their ability to detect a normal WEST filament or PSSD within a normal force range. Our study was limited by a small sample with healthy participants.