Performance Analysis and Clinical Evaluation of an Automated Tool for Plantar Threshold Sensitivity Assessment in a Non-Diabetic Control Population

Abstract

Neuropathy is associated with sensation loss in the extremities. Semmes–Weinstein monofilaments are common tools used to assess an individuals' sensation perception. It has long been characterized using hand-applied Semmes–Weinstein monofilaments, however they are subjected to clinician biases and material deviations, and other factors that affect the reproducibility to administer a consistent amount of contact force on the plantar surface. A tool was developed to automate this testing protocol and to more accurately determine an individual's threshold sensitivity at various locations on the plantar surface. Individuals without type 2 diabetes mellitus (DM2) were classed as control subjects. They were evaluated using a hand applied monofilament and the automated tool. The device accuracy of the automated tool was first determined, followed by subject's threshold sensitivity at each location. Twenty-six locations were evaluated per person between 0.35 and 10.0 grams-force. A threshold sensitivity index norm was calculated based on the threshold sensitivity at each location per individual and was plotted against age, body mass index, ankle brachial index, fasting blood sugars, and HbA1c. The device demonstrated accuracy with an absolute error less than or equal to 0.4 grams-force at most locations. Age showed the strongest relationships to sensation loss. As age increased sensitivity to touch decreased. The automated tool was shown to be effective in determining an individual's threshold sensitivity in individuals without DM2. The calculation of the threshold sensitivity index norm was useful to classify sensation loss. The automated tool has the potential to effectively diagnosis neuropathy and document disease progression.