--but they are generally inspecific for small-fiber neuropathy, which is why the skin biopsy has become the gold standard test. If fact, many people, such as myself, had completely normal tests (in my case, a hundred pages of them) until the skin biopsy revealed the actual damage to the nerves.

Gradual onset diabetic/impaired glucose neuropathy and celiac/gluten sensitivity neuropathy are typically small-fiber in presentation, and there are blood test for these, of course. And a number of hereditary and toxic neuropathies selectively attack small fibers, and these can be tested for (if a neurologist or other doctor is even aware of it). Some autoimmune conditions that there are blood tests for also have small-fiber involvement.

Still, it's possible--and common--to show small fiber damage on skin biopsy and not be positive or abnormal on any of those blood tests. It's why so many small-fiber sufferers are "idiopathic".