SLR - August 2015 - Yekaterina Narodetskaya

Sensitivity and Specificity of a New Test for Thermographic Evaluation of the Foot in the Diagnosis of Diabetic Peripheral Polyneuropathy

Reference: García-De-La-Peña R, Benhamú S, Munuera PV. Sensitivity and Specificity of a New Test for Thermographic Evaluation of the Foot in the Diagnosis of Diabetic Peripheral Polyneuropathy. Adv Skin Wound Care. 2014 Nov;27(11):491-8

Scientific Literature Review

Reviewed By: Yekaterina Narodetskaya, DPM
Residency Program: Wyckoff Heights Medical Center

Podiatric Relevance: The study undertaken in this article is greatly advantageous for the podiatric field. Identifying neuropathic patients is key in prevention and treatment of podiatric pathology. With this study, the authors undertook the challenge of testing the validity of a novel test for detection of neuropathy by testing whether the inability to discern temperature changes was correlated to neuropathic disease. Their hypothesis was demonstrated to be correct. With previous tests which check for vibratory proprioception or the SW MF 5.07 test, the patient is deemed either neuropathic or not. This test allows physicians to numerically assess the neuropathic status of each patient changing this from a categorical to an incremental type of pathology. Additionally, the authors’ finding that neuropathic feet have an increase in basal temperature is invaluable, as it is not subject dependent. Often, in the podiatric routine clinical exam, neuropathy cannot be assessed if the patient cannot voluntarily respond, both of which the vibratory proprioception and the SW MF 5.07 test require.

Methods: Thirty-five patients with diabetes mellitus were included in the study. They were divided into two groups: neuropathic and non neuropathic. A 10g SW MF 5.07 was applied to the plantar great toe, first metatarsal head, and fifth metatarsal head. Inability to note the monofilament at one or more locations indicated a lack of protective sensation. The subjects were held in a constant, thermal controlled setting where a neurologic examination was performed. A thermal sensitivity examination was then performed testing thermal discrimination threshold and thermal sensitivity. A thermometer probe was placed on dorsal aspect of each subject’s foot, recording the temperature. A two faced hammer was then placed on one of three innervation zones at random: dorsal aspect of the foot, plantar first metatarsal head, and plantar fifth metatarsal head. One face registered the basal temperature of the foot, while the other altered the recorded temperature in increments of 0.5 degrees Celsius, until the participant sensed a change and had to identify whether it was warmer or cooler.

Results: The examiners found that a decrease in thermal discrimination was consistent with a decrease in protective sensation as tested by the SW MF 5.07. The first and fifth metatarsal heads were both areas suitable to predict neuropathy via thermal examination. In both areas 2 degrees Celsius was the value determined to predict neuropathy. Also, the authors found that all neuropathic patients had greater basal foot temperatures by an average of 1.5 degrees Celsius, and required greater temperature differences in both cool and warm differences in order to sense change. A higher statistical significance was noted in the neuropathic patient’s ability to detect changes with warm temperatures versus cold. Although a higher HbA1C value had no correlation with temperature perception, it did present with a higher basal temperature.

Conclusion: The authors applied the Peltier effect in this study to create a diagnostic tool for assessment of diabetic polyneuropathy. The thermal perception test was deemed to be an appropriate test in early diagnosis of early diabetic polyneuropathy, as in comparison with SW MF 5.07 test, a test that is regarded by many as the criterion standard for this diagnosis. The authors argue that due to the higher statistical significance, only thermal discrimination for warmth should be utilized in evaluating for neuropathy. Additionally, both the first and the fifth metatarsal heads had positive predicative value, and the same quantitative number of 2 degrees as the value necessary to diagnose neuropathy.  From this study, we can conclude that thermal evaluation is a useful exam that can be used for detection of neuropathy. Utilizing this test on patients in the routine clinical setting can advance podiatric care and prevent future pathology in the neuropathic patient.

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