Contribution of QSART to the diagnosis of small fiber neuropathy

Abstract

We evaluated incorporation of the quantitative sudomotor axon reflex test (QSART) into the diagnostic criteria for small fiber neuropathy (SFN) as an addition to quantitative sensory testing (QST) and intraepidermal nerve fiber density (IENFD) testing. One hundred one patients with clinically suspected SFN underwent QSART, QST, and skin biopsy. The diagnostic yield of existing SFN criteria in these patients was compared with criteria incorporating QSART. The new combined diagnostic criteria were evaluated. SFN was diagnosed in 38 of the 101 patients (38%) using current criteria. Addition of QSART existing SFN criteria resulted in an increased diagnostic yield to 67 patients (66%). Applying new SFN criteria requiring abnormality in at least 2 assessments among QSART, QST, and IENFD resulted in a diagnosis of SFN in 57 patients (56%). Assessment of both somatic and peripheral autonomic small nerve fibers enhances diagnostic criteria for SFN.