Getting started:
Skin biopsy for Small Fiber Neuropathy

Demonstration of a reduction in the Epidermal Nerve Fiber Density (ENFD) on punch skin biopsy is a highly sensitive and specific test for Small Fiber Neuropathy (SFN)1. Therapath provides testing kits to physicians at private practices, hospitals, and Military and VA health facilities across the country.


Ordering a biopsy kit

Biopsy kits can be ordered by telephone (800.681.4338), or by emailing

Kits are provided at no charge and are shipped via overnight service. They can be ordered well in advance of the biopsy, or just a few days before the procedure.



Biopsy supplies

Therapath provides everything needed to perform a skin biopsy except 2% lidocaine, a syringe, and gloves.

When your biopsy kit arrives, unpack it immediately. Save the blue box, cooler, paperwork, and biopsy tools. Keep the cold pack for return shipping, all specimens must be shipped cold.

Please store the fixative vials according to the instructions on the biohazard bag and note the expiration date of the fixative.


The following biopsy tools are provided with each kit:

1.  3mm punch biopsy tool with specimen ejector
2.  Metal scissors
3.  Metal forceps
4.  Two 2ml specimen vials with fixative
            a. Extra vials available by request 
            b. Two fixative types available 
5.  Cold pack for return shipping
6.  Alcohol prep pads
7.  Iodine prep pads
8.  2 full size adhesive bandages and gauze



Man LabelsBiopsy site selection

In patients with suspected neuropathy, skin samples are obtained by skin punch biopsy. Standard sites in the lower extremity include the foot, distal leg (calf), and proximal thigh.

For patients with symptoms in the upper extremity, standard sites include the proximal and distal arm. For patients 18 years and older, Therapath has established normal values by gender and age for both ENFD and SGNFD at all five sites. These values allow Therapath to provide a result that is both quantitative and diagnostic for small fiber neuropathy.

If focal neuropathy is suspected, a biopsy sample in the distribution of the affected nerve can be compared to the corresponding site on the non-affected side of the body.

The same biopsy sample can be used for both Epidermal Nerve Fiber Density and Sweat Gland Nerve Fiber Density.



Biopsy procedure

  • Make a 1 cm circle around the biopsy site. Clean the skin with an alcohol swab. Anaesthetize skin with 2% lidocaine with epinephrine by injecting the edge of the circle, infiltrating but avoiding direct contact with the biopsy site, in order to form a bleb.
  • The biopsy is performed using a 3 mm circular punch, at a depth of 4 mm, or almost the full distance of the metal head of the punch tool. Push the tool with rotational motion and even pressure into the epidermis.
  • Lift the edge of the biopsy with the anaesthetizing needle or forceps and free the biopsy from the attached underlying fatty tissue using forceps or scissors.


  • Forceps should never contact the upper layer of the skin, but only the underlying tissue as it might destroy nerve fibers.
  • Immediately place one sample in each vial of fixative and verify that the sample is floating before sealing the vial securely.
  • Label the vials with the patient’s name using the appropriate body site stickers from the provided requisition form. Place vials in the included specimen bag.



Return shipment to Therapath


Specimens must be shipped the same day they are collected.

Place the frozen cold pack in the cooler with the foam barrier on top. Deposit the specimen bag with labeled vial(s) on top of the foam barrier.

Close the foam cooler and place it in the blue cardboard box. Enclose the completed requisition form and copy of the patient’s insurance card inside the blue box.


  • UPS customers should place the kit in a pre-paid return pack and contact UPS at 800.823.7459
  • FedEx customers should place the kit in a pre-paid return pack and contact FedEx at 800.463.3339



You’re all done!

Thank you for sending a specimen to Therapath. We will receive the sample the next day and begin processing. Results for Epidermal Nerve Fiber Density testing will be available in 7-10 days. Please allow an additional 7 days for sweat gland results. 

If you have any questions or comments, we would love to hear from you:



1. Periquet et al, 1999; Ebenezer et al, 2007; Lauria et al, 2010; Hays et al, 2010


How can we help you?

Are you interested in using Therapath at your practice? Our client services team is available to speak with you.

Contact us

Request a kit