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

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.

An initial evaluation of a proof-of-concept 128-Hz electronic tuning fork in the detection of peripheral neuropathy.

BACKGROUND: Diabetic peripheral neuropathy (DPN) is an essential precursor leading to diabetic limb loss. Neurologic screening tests, including the 128-Hz tuning fork (TF), have long been used to identify and track the progression of DPN, thereby guiding the implementation of preventive strategies. Although a sensitive indicator of neuropathy, shortcomings of TF testing include the lack of standardization and quantification of clinical findings. In an attempt to overcome these limitations, a novel 128-Hz electronic TF (ETF) prototype has been developed that is capable of performing accurate timed vibration tests (TVTs). This study was designed to assess the ability of the ETF to detect sensory impairment compared with three established neurologic screening methods: the Semmes-Weinstein monofilament test, the biothesiometer, and the sharp/dull discrimination test. METHODS: Fifty-five test patients were recruited from the primary author's practice and enrolled according to an approved protocol. The 10-g Semmes-Weinstein monofilament test and the sharp/dull discrimination test were administered in standard fashion to the plantar aspects of digits 1 and 5 bilaterally. The ETF and the biothesiometer (25-V setting) were applied to the dorsal aspects of the distal phalanx of the hallux and fifth metatarsal head bilaterally. RESULTS: The sensitivity and specificity of neuropathy detection for the ETF were 0.953 and 0.761, respectively, using conventional tests as reference standards. CONCLUSIONS: Performance of TVTs with the ETF detected sensory impairment compared with three conventional neurologic screening methods. Given these findings, the ETF could facilitate the use of standardized TVTs as an indicator of DPN progression.

Relative sensory sparing in the diabetic foot implied through vibration testing.

BACKGROUND: The dorsal aspect of the hallux is often cited as the anatomic location of choice for vibration testing in the feet of diabetic patients. To validate this preference, vibration tests were performed and compared at the hallux and 5th metatarsal head in diabetic patients with established neuropathy. METHODS: Twenty-eight neuropathic, diabetic patients and 17 non-neuropathic, non-diabetic patients underwent timed vibration testing (TVT) with a novel 128 Hz electronic tuning fork (ETF) at the hallux and 5th metatarsal head. RESULTS: TVT values in the feet of diabetic patients were found to be reduced at both locations compared to controls. Unexpectedly, these values were significantly lower at the hallux (P<0.001) compared to the 5th metatarsal head. CONCLUSION: This study confirms the hallux as the most appropriate location for vibration testing and implies relative sensory sparing at the 5th metatarsal head, a finding not previously reported in diabetic patients.