Using a Variety of Modalities to Measure Both Small and Large Fiber Neuropathy Provides More Accurate Estimates of the Prevalence of Diabetic Neuropathies

In April 2024, the Journal of Diabetes and Its Complications published “Contemporary prevalence of diabetic neuropathies in individuals with Type 1 and Type 2 diabetes in a Danish tertiary outpatient clinic”, a large scale study from researchers at the Steno Diabetes Center in Copenhagen, Denmark. Researchers assessed 822 individuals with Type 1 and 899 individuals with Type 2 diabetes for both distal symmetric polyneuropathy (DPN) and diabetic autonomic neuropathy (DAN) using a variety of modalities in order to make population-based prevalence estimates.

Where they exist, past estimates of various neuropathies have shown wide ranges of prevalence. In the Steno study, DPN was assessed using vibration perception threshold (VPT), sural nerve function, touch, pain, and thermal sensation. DAN was assessed using cardiovascular reflex tests, electrochemical skin conductance, and gastroparesis cardinal symptom index.

Batteries of DPN methods were applied for 4 groups by adding modalities to each group from large fiber neuropathy with VPT above 25 V and/or abnormal touch sensations (reflecting how DPN is currently assessed in a diabetes clinic setting) to VPT using age-height-sex specific cutoffs, to sural nerve conduction, and finally to small fiber neuropathy as measured by Sudoscan in the feet, abnormal pain and/or abnormal thermal sensation. For DAN, Sudoscan was used to evaluate sudomotor function as measured by electrochemical skin conductance in the feet and hands along with cardiovascular autonomic neuropathy measured by a Vagus device, and orthostatic hypotension based on supine and standing blood pressure.

Prevalence of DPN varied depending on the modalities applied for Type 1 and Type 2 diabetes. Including small fiber neuropathy as measured by Sudoscan increased the prevalence of definite DPN diagnosed by Toronto consensus criteria, from 46 to 54% for Type 1 and from 54 to 68% for Type 2. In contrast, monofilament had the lowest overlap with other diagnostic modalities. Touch sensation showed the lowest prevalence of DPN, perhaps because it can only measure more severe neuropathy. The prevalence of DPN measured by Sudoscan in the feet was twice as high for Type 1 diabetes and 10% higher for Type 2 as the commonly used VPT above 25 V.

Assessing both large and small fiber neuropathy using a variety of modalities was found to be the best way to increase the prevalence of DPN and DAN diagnoses. Measuring small fiber neuropathy was recommended by the researchers for early detection. Small fiber neuropathy, they noted, is not detected using the tools commonly used in diabetes care today.

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