Effectiveness of Current Diagnostic Methods in the Early Detection of Diabetic Peripheral Neuropathy: Are We Missing the Window?

Diabetic peripheral neuropathy (DPN) is one of the most common long-term complications of diabetes and a major cause of foot ulceration, pain, balance impairment, and lower-limb amputation. Nerve injury may begin early, but many patients remain undiagnosed until they already have clinically important sensory loss. A major reason is that early neuropathic change may involve small sensory and autonomic fibers, whereas routine clinic screening is largely designed to identify established large-fiber dysfunction and loss of protective sensation. This narrative review evaluates the strengths and limitations of current diagnostic methods for DPN and considers whether routine practice misses the optimal window for early detection. For transparency, the literature was narratively reviewed using PubMed/MEDLINE (Medical Literature Analysis and Retrieval System Online), Scopus, and Google Scholar, focusing mainly on English-language studies, guidelines, landmark trials, and review articles published between 2000 and March 2026, while also including older seminal papers where relevant. Search terms covered DPN, diabetic sensorimotor polyneuropathy, small-fiber neuropathy, corneal confocal microscopy, skin biopsy, quantitative sensory testing, sudomotor testing, point-of-care nerve conduction, neurofilament light chain, prediabetes, metabolic syndrome, screening, diagnosis, and guidelines. We reviewed bedside screening tools, structured clinical scores, nerve conduction studies, and newer approaches that assess small-fiber damage, including skin biopsy, corneal confocal microscopy, quantitative sensory testing, and sudomotor assessment. We also discuss point-of-care nerve conduction devices, autonomic testing, emerging blood biomarkers, and wearable technologies. Traditional bedside tools such as the 10 g monofilament and vibration testing remain essential for ulcer-risk assessment, but their sensitivity for early disease is limited. Nerve conduction studies are useful for confirming large-fiber neuropathy and excluding alternative diagnoses, yet they may remain normal in early or predominantly small-fiber disease. Methods that focus on small-fiber pathology have shown promise for earlier detection, but broader implementation is restricted by cost, access, training requirements, variable standardization, and limited outcome data showing that earlier detection consistently changes long-term endpoints. No single test is ideal. In current practice, the most realistic strategy is a risk-based, multimodal approach: continue universal annual screening for all people with diabetes, distinguish clearly between screening for ulcer risk and diagnosing neuropathy, take symptoms seriously even when routine tests are normal, and refer selected symptomatic or high-risk patients for further assessment where small-fiber testing is available.