Originally Posted by echoes long ago

there should be a written record of what your nerve density was. it is part of the procedure to calculate that percentage.

http://www.ccjm.org/content/76/5/297.full

This is from the Cleveland Clinic Journal of Medicine

Skin biopsy
Skin biopsy is a minimally invasive procedure in which 3-mm-diameter punch biopsy specimens are taken from the distal leg, distal thigh, and proximal thigh of one lower limb. The procedure takes only 10 to 15 minutes.

Biopsy specimens are immunostained using an antibody against protein gene product 9.5, which is a panaxonal marker. Small nerve fibers in the epidermis are counted under a microscope, and intraepithelial nerve fiber densities are calculated and compared with established normative values. The diagnosis of small fiber neuropathy can be established if the intraepidermal nerve fiber density is lower than normal (FIGURE 1). Nerve fiber density may be normal in the early stage of small fiber neuropathy, but in this setting skin biopsy often shows abnormal morphologic changes in the small fibers, especially large swellings,24 and repeat biopsy in 6 to 12 months may be considered.

The diagnostic efficiency of skin biopsy is about 88%.21,23 For diagnosing small fiber neuropathy, it is more sensitive than quantitative sensory testing21,25 and more sensitive and less invasive than sural nerve biopsy.26 Intraepidermal nerve fiber density also correlates well with a variety of measures of severity of HIV distal sensory neuropathy and thus may be used to measure the severity and treatment response of small fiber neuropathy.27