Biothesiometer Testing

This compact device consists of a handpiece with a rubber tactor that vibrates at 100 Hz (Xilas Medical, San Antonio Texas, USA). The hand-held unit is connected by an electrical cord to a breadbox-sized base unit. This unit contains an analog scale which displays the applied voltage, ranging from 0 to 50 Volts. The device is simply held with the tactor balanced vertically at the distal aspect  of the toe. At this time, the voltage is increased on the base unit until the patient perceives a vibration. This value, measured in Volts, is termed the “vibration perception threshold”, or VPT.

Semmes Weinstein (SW) monofilament test

The SW testing may be carried out using a simple “yes-no” method of administration. This method is employed by instructing the patient to say “yes” each time that he or she perceives the application of the monofilament. Measurements were taken at each of ten sites on the foot. The ten sites tested include the first, third and fifth digits, plantarly, the first, third, and fifth metatarsal heads plantarly, the plantar midfoot medially and laterally, the plantar heel, and the midfoot, dorsally.

The lack of perception of 4 or more out of 10 sites on the bottom of the foot using the SWMF carried with it a 97% sensitivity and a 83% specificity in identifying patients at highest risk for diabetic foot ulcers. This was the optimum combination of sensitivity and specificity for this device.   Another device commonly used in diabetic foot specialty clinics, the Biothesiometer measures vibration perception (also known as vibration perception threshold). The optimum vibration perception threshold was 25 volts yielding a 90% sensitivity and 84% specificity. When these diagnostic modalities were combined (with either one or both positive on physical exam), the sensitivity rose to 100% with a specificity of 77%. Clearly, a combination of modalities leads to a more sensitive (and not significantly less specific) screening tool. 


Armstrong, et al: Choosing a practical screening instrument to identify patients at risk for diabetic foot ulceration. Arch Intern Med, 148:289-292, 1998

Testing for Loss of Proctection Sensation (LOPS)