Early detection of diabetic peripheral neuropathy using EMLA-induced skin wrinkling

Background & Objective: Screening for early diabetic peripheral neuropathy (DN) is essential for foot ulcer prevention. The Semmes–Weinstein monofilament (SWMF) is commonly used to detect DN in Thailand. However, SWMF interpretation requires patient participation, which is susceptible to risk of error in patients with impaired cognitive function or uncooperative patients. In contrast, stimulated skin wrinkling (SSW) can be interpreted by trained investigators, which is more appropriate. This study aimed to investigate the utility of SSW using a eutectic mixture of local anesthetic (SSW-EMLA) for early DN diagnosis. Methods: This cross-sectional study, recruited 102 patients with diabetes (DM group), 33 with diabetes with foot ulcer (DN control group), and 30 without diabetes (non-DN control group) from the Faculty of Medicine, Vajira Hospital, Navamindradhiraj University, Thailand, from February 3, 2021 to November 30, 2021. SSW was conducted by applying EMLA on the tips of the 2nd, 3rd, and 4th fingers of both hands. SWMF, sensory perception of pain (SPP), vibration perception threshold (VPT), joint position sense (JPS), and deep tendon reflexes (DTR) were also evaluated on the same day. Results: The Interrater agreement of two investigators for SSW-EMLA was high with intraclass correlation coefficients of 0.87 (0.824–0.904) for the right hand and 0.874 (0.830–0.907) for the left hand. The kappa coefficients of agreement of SSW-EMLA for SPP, SWMF, VPT, JPS, and DTR testing were 0.411, 0.478, 0.714, 0.444, and 0.681, respectively. The sensitivity and specificity of SSW-EMLA testing for DN detection were 83.3%, was 85.7%, respectively. Conclusion: The SSW-EMLA test can be considered as an alternative method for DN detection, due to its noninvasiveness, inexpensiveness (50THB), being a simple procedure, high sensitivity and specificity, and acceptable rater variation.