Small fiber neuropathy is a painful neuropathy that cannot be assessed using nerve conduction studies. A skin biopsy and quantitative sensory testing (QST) are the gold standards for small fiber neuropathy diagnosis. However, a skin biopsy is invasive and commercially unavailable in Korea. QST is a method involving a thermal threshold, but its results can be affected by cognition as well as lesions of the central nervous system. Quantitative sudomotor axon reflex test (QSART) is a quantitative method of assessing sweat glands innervated by small fibers. In this review, we assessed the utility of QSART in evaluating small fiber neuropathy.

Citations

• Diagnostic Performance of Infrared Thermography, Quantitative Sudomotor Axonal Reflex Testing, and 3-Phase Bone Scintigraphy for Complex Regional Pain Syndrome Diagnosis: A Retrospective Observational Study
  Chan Noh, Jiyong Lee, Hye Young Choi, Eunhye Park, Yong Sup Shin, Boohwi Hong, Youngkwon Ko, Chahyun Oh, Sun Yeul Lee
  Journal of Pain Research.2025; Volume 18: 1305.     CrossRef

Diabetic polyneuropathy (DPN) causes neuropathic pain with reduced quality of life as well as diabetic foot ulceration which sometimes resulted in amputation. Early detection and improved knowledge of pathogenic pathways are important to prevent and to manage DPN. The screening methods and several tests to diagnose DPN-quantitative sensory testing, skin biopsy, corneal confocal microscopy, etc.-will be described.

Background
Although quantitative sensory test (QST) is being used with increasing frequency for measuring sensorythresholds in clinical practice and epidemiologic studies, there has been no age-matched normative data in Korean adults.The objective of this study is to evaluate the value of QST in diabetic polyneuropathy with normal range in Korean adults.Methods: The Computer Aided Sensory Examination IV 4,2 (WR Medical Electronics Co., Stillwater, Minnesota, U.S.A.),with 4,2,1 stepping algorithm was used to determine vibration and cold perception threshold in 70 normal controls and 19patients with diabetic polyneuropathy aged from 21 to 79 years. The data were used to define age-matched upper and lowernormal limits and normal range of side to side difference. We also evaluated the duration of diabetes, serum HbA1C level,and findings of nerve conduction study (NCS) and QST in patients with diabetic polyneuropathy. Results: In normal adults,sensory thresholds slightly increased with age, and a slight side-to-side difference was observed. The diagnostic sensitivityof QST was not higher than NCS in patients with diabetic polyneuropathy (36.8% vs. 42.1%, p=0.716), especially amongelderly patients. Conclusions: QST might be used as a complementary test for NCS in the diagnosis of diabeticpolyneuropathy. Although the QST is a simple method for the evaluation of peripheral nerve function, there are somelimitations. Most of all, because the QST measuring is dependent on the subjective response of patients, the degree of concentrationand cooperation of the patients can significantly affect the result. And thus, attention should be paid during theinterpretation of QST results in patients with peripheral neuropathy.