Background: In order to meet the diagnostic criteria of small fiber neuropathy (SFN), intraepidermal nerve fiber density measurement by skin biopsy or quantitative sensory test (QST) should be performed. Though sensory symptoms alone should not be considered a reliable screening feature, these tests are only available at specialized centers. Although questionnaires have the benefit of being quick and simple to complete, there are still few research on the value of them in the diagnosis of SFN. The aim of our study is to ascertain whether the small fiber neuropathy and symptom inventory questionnaire (SFN-SQ) or the PainDETECT can be used to screen for SFN.

 

Methods: Sixty-seven patients who showed clinical symptoms of SFN and performed nerve conduction study and QST were evaluated. When a threshold for cold or heat pain exceeds 95 percentile with a normal vibration threshold, it was referred to as QST (+), and all thresholds above 95 percentile are referred to as QST (mixed). We defined as NCS (+) and NCS (-) according to the presence or absence of abnormalities in the sensory nerve conduction study. Patients were divided into three groups according to test abnormalities: (1) NCS (-)/QST (+), (2) NCS (-)/QST (mixed), and (3) NCS (+)/QST (mixed). The cut-off values of SFN-SIQ and painDETECT was 6.5 and 13 points, respectively, as defined in the previous studies.

 

Results: The sensitivity of SFN-SIQ was 80% in group 1 (n=15), 80.8% in group 2 (n=26) and 69.2% in group 3 (n=26), while the sensitivity of painDETECT was 60%, 57.5% and 57.5% in group 1, 2, and 3, respectively.

 

Conclusion: SFN-SIQ demonstrated greater sensitivity in SFN than in mixed neuropathy, so it is likely to be useful as an SFN screening tool.