Objective: To determine the usefulness of Eutectic Mixture of Local Anesthetic (EMLA)-induced stimulated skin wrinkling (SSW) to detect diabetic sensorimotor polyneuropathy (DSPN).
Research design and methods: Two hundred and ten diabetics were prospectively recruited (mean age 58.5 ± 12.7 years) from a large tertiary center from 2009 to 2011. EMLA was applied to the tips of digits 2, 3, and 4 and the degree of wrinkling graded. Diabetic Neuropathy Symptom (DNS) score, nerve conduction studies (NCS), Semmes-Weinstein monofilament (SWMF) tests, and vibratory perception thresholds (VPTs) testing were chosen as comparative clinical standards to diagnose length-dependent DSPN.
Results: Inter-rater agreement for two examiners of SSW was high, with Cohen's weighted κ of 0.912 for the right hand, and 0.823 for the left. K measure of agreement of SSW with the NCS, DNS scores, SWMF testing, and VPT testing was 0.486, 0.243, 0.289, and 0.395 respectively. SSW was able to distinguish between normal and abnormal NCS and DNS results, with median scores of 3.333 vs. 1.667 (p < 0.0005); and 3.167 vs. 2.000 (p < 0.0005) respectively. Following receiver operating characteristic-analysis, at a cut-off point of <3 for an abnormal SSW test, sensitivity of SSW test for diagnosing DSPN using NCS as a reference standard was 81.3%, and specificity was 67.0%, on par with other testing methods.
Conclusion: SSW shows comparable sensitivity to other methods for detecting DSPN. Given its low cost and easy administration, SSW can be considered a useful alternative screening method for diagnosing diabetic neuropathy.
Keywords: EMLA; diabetic polyneuropathy; nerve conduction study; skin wrinkling; water-immersion wrinkling.