Peripheral Nerve Society Guideline on processing and evaluation of nerve biopsies.

Nerve biopsy is often the final step in the diagnostic work-up of neuropathies of unknown origin. The aim of this guideline was to prepare an evidence-based guideline on the methods for performing and evaluating nerve biopsy. The panel performed a search of MEDLINE, hand search of bibliographies of the references retrieved, review of the evidence, and reached agreement by consensus. There were not enough formal studies of diagnostic test accuracy to allow evidence-based recommendations of levels A-C for most questions. The panel summarized the class IV evidence and reached agreement by consensus on the following recommendations: (1) Nerve biopsy should not be performed before adequate clinical, electrophysiological, and laboratory investigation and only be performed with appropriate informed consent. (2) An interactive working relationship with the relevant disciplines involved and the provision of sufficient clinical information is encouraged. (3) Biopsies should be processed and read by professionals with adequate training and experience. (4) Optimal analysis of nerve biopsy is best performed by laboratories that have the facilities and expertise to prepare and evaluate frozen and fixed sections (cryostat, paraffin, and epoxy sections). (5) Immunohistochemistry, teased fiber analysis, electron microscopy, and morphometry may help clarify the diagnosis in some conditions and should be considered as additional studies.