Combined Utility of the Semmes-Weinstein Monofilament and the Timed Vibration Test in the Prediction of Diabetic Foot Ulcers

Abstract

Background: Neurologic screening tests are often used to identify and stratify patients at risk for diabetic foot complications such as infections, ulcers, and amputations. Two of the most commonly cited methods are the 5.07 Semmes-Weinstein monofilament (SWM) for loss of protective sensation and vibratory sensation testing. The aim of this study was to determine whether combined SWM and the timed vibration test (TVT) more effectively predicts diabetic foot ulcer (DFU) development compared with each test alone. Methods: An electronic medical record database search was performed restricted to podiatric medical clinic patients with diabetes and DFU ICD-10 diagnosis codes. Of 200 patients who met the criteria, 24 developed DFUs. A statistical analysis was performed comparing the SWM and TVT at various cutoff times and the combined SWM/TVT in their ability to predict DFUs. Results: Statistical analysis revealed that the TVT cutoff time of less than 4 sec was superior to the other times for prediction of DFUs. The combined SWM/TVT results at less than 4 sec were superior to each test individually: sensitivity, 87.5%; specificity, 84.7%; positive predictive value, 43.8%; and receiver operating characteristics area under the curve, 0.86. Conclusions: The SWM combined with TVT was shown to be superior compared with either test alone in discriminating DFU risk. In addition, the TVT cutoff time of less than 4 sec proved to have greater diagnostic yield than other times, including 0 sec. This unexpected finding might impact providers relying on the absence of vibration sensation via tuning fork testing as an optimal marker of DFU risk.