A comparison of the monofilament with other testing modalities for foot ulcer susceptibility

We studied the number of testing sites and the proportion needed to be insensate for the optimal assessment of foot ulcer risk with the 10 g monofilament. Also, we compared the sensitivity and specificity of the 10 g monofilament with other methodologies. Fifty-two individuals with either a current foot ulcer, a history of a foot ulcer or the presence of Charcot neuroarthopathy and 51 individuals with no history of any of these conditions were assessed with the 10 g monofilament at four sites on each foot, the 128 Hz tuning fork at the halluces, the Biothesiometer at the halluces and the modified neuropathy disability score. Sensitivities and specificities were calculated for the various modalities. The Biothesiometer and the neuropathy disability score had the highest sensitivities (0.92 for both). The 128 Hz tuning fork tested only at the halluces (criterion: ≥1 insensate site) had the same sensitivity (0.86) as the 10 g monofilament tested at eight sites (criterion: ≥1 insensate site) with similar specificities (0.56 and 0.58, respectively). The Biothesiometer and the modified neuropathy disability score tend to be more sensitive than the 10 g monofilament for the assessment of individuals at risk for foot ulcers. The 128 Hz tuning fork tested at only two sites is as sensitive as the 10 g monofilament tested at eight sites. These data suggest that the 10 g monofilament may not be the optimum methodology for identifying individuals at risk of foot ulcers.