My pain is getting worse...

Is it possible that a Sensory Neuropathy cannot be detected when its in the early stage? Is it a disease that is "building up" before it shows in the test?

With my pain getting worse, I cannot help but think if my specimen was mixed up with someone else's.

Has there been anyone who had a negative skin biopsy but later on re-tested and was positive? In this case, how many months should be the interval before getting another test (assuming doctor and insurance will allow).

Thank you.