Intraepidermal nerve fiber density and its application in sarcoidosis.
BACKGROUND
Intraepidermal nerve fiber density (IENFD) is considered a good diagnostic tool for small fiber neuropathy (SFN).


OBJECTIVE
To assess stratified normative values for IENFD and determine the reliability and validity of IENFD in sarcoidosis.


METHODS
IENFD was assessed in 188 healthy volunteers and 72 patients with sarcoidosis (n = 58 with SFN symptoms, n = 14 without SFN symptoms). Healthy controls were stratified (for age and sex), resulting in 6 age groups (20-29, 30-39, ... up to > or = 70 years) containing at least 15 men and 15 women. A skin biopsy was taken in each participant 10 cm above the lateral malleolus and analyzed in accordance with the international guidelines using bright-field microscopy. Interobserver/intraobserver reliability of IENFD was examined. In the patients, a symptoms inventory questionnaire (SIQ; assessing SFN symptoms) and the Vickrey Peripheral Neuropathy Quality-of-Life Instrument-97 (PNQoL-97) were assessed to examine the discriminative ability of normative IENFD values.


RESULTS
There was a significant age-dependent decrease of IENFD values in healthy controls, with lower densities in men compared with women. Good interobserver/intraobserver reliability scores were obtained (kappa values > or = 0.90). A total of 21 patients with sarcoidosis had a reduced IENFD score (< 5th percentile; 19 [32.8%] in patients with SFN symptoms, 2 [14.3%] in patients without SFN symptoms). The validity of the normative IENFD values was demonstrated by distinguishing between the SIQ scores and various PNQoL-97 values for the different patient groups.


CONCLUSIONS
This study provides clinically applicable distal intraepidermal nerve fiber density normative values, showing age- and sex-related differences.
Bakkers
M
M
Department of Neurology, Maastricht University Medical Centre, PO Box 5800, 6202 AZ, Maastricht, The Netherlands. m.bakkers@mumc.nl
Merkies
I S J
IS
Lauria
G
G
Devigili
G
G
Penza
P
P
Lombardi
R
R
Hermans
M C E
MC
van Nes
S I
SI
De Baets
M
M
Faber
C G
CG
D000328:Adult; D000367:Age Factors; D000368:Aged; D001706:Biopsy; D016022:Case-Control Studies; D004817:Epidermis / Q000294:innervation*; D005260:Female; D006801:Humans; D008297:Male; D008853:Microscopy; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D010523:Peripheral Nervous System Diseases / Q000209:etiology* / Q000473:pathology*; D011788:Quality of Life; D015203:Reproducibility of Results; D012507:Sarcoidosis / Q000150:complications* / Q000473:pathology; D012737:Sex Factors; D011795:Surveys and Questionnaires