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The diagnostic accuracy of Sudoscan in TTR-FAP


Small-fibre length-dependent sensory-motor and autonomic neuropathy is the hallmark of TTR-FAP.

SUDOSCAN was recently introduced as a quick and non-invasive method that measures electrochemical skin conductance (ESC) of palmar and plantar surfaces, through reverse iontophoresis. It has been described as a promising diagnostic tool in distal symmetric polyneuropathies, such as diabetic small fibre neuropathy.


To evaluate the diagnostic accuracy of Sudoscan in patients with TTR-FAP.


Forty stage I TTR-FAP patients were compared with 70 TTR-FAP asymptomatic carriers and 37 healthy controls, matched for age, gender and body-mass index. Inclusion criteria for TTR-FAP patients included normal sural nerve sensory action potential amplitude and plantar sympathetic skin response (SSR). Patients with diabetes were excluded. All subjects were assessed with Sudoscan in hands and feet, bilaterally.


Feet ESC was significantly reduced in Stage I patients compared with asymptomatic carriers and controls (57.8 ± 24.3 vs 76.5 ± 7.8 and 79.7 ± 5.1; p < 0.000). Hands ESC did not show significant difference between groups.

Receiver operating characteristic curve analysis revealed an area under the curve of 0.80 for the plantar ESC.

A significant correlation was found between plantar and Sural nerve action potential amplitude (0.320; p < 0.001).


Sudoscan seems to be a promising diagnostic tool in TTR-FAP patients with normal conventional nerve conduction studies and preserved plantar SSR. However, its predictive value is unknown.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Castro, J., Conceicao, I., Castro, I. et al. The diagnostic accuracy of Sudoscan in TTR-FAP. Orphanet J Rare Dis 10 (Suppl 1), P42 (2015).

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