Normative Data and Quantile Regression Analysis of the Sural-to-Radial Nerve Amplitude Ratio

Abstract

Purpose: The aim of this study was to establish normative data for the sural-to-radial nerve amplitude ratio (SRAR) and develop a quantile regression model for individualized cutoff values. Methods: A cohort of 68 healthy individuals (36 female participants) aged 20 to 59 years was recruited. Sensory nerve conduction studies were conducted to measure sural and radial sensory nerve action potential amplitudes. Quantile regression analysis was used to determine the fifth percentile of SRAR after adjusting for age, sex, and other demographic variables. Results: This study found significant differences in body height and weight between the sexes, with radial sensory nerve action potential being higher in female participants. The sural-to-radial nerve amplitude ratio was negatively correlated with age (r = −0.3, p = 0.007) and showed significant sex differences. The final regression equation, SRAR = 0.519 − 0.006 × age + 0.046 × sex (1 = male, 0 = female), was developed for the fifth percentile cutoff, accounting for age and sex. Conclusions: This study establishes normative SRAR data and introduces a novel quantile regression approach to determine individualized cutoff values. Age and sex are critical factors for SRAR variation, necessitating tailored diagnostic criteria for neuropathy assessment. This model enhances diagnostic accuracy and potentially reduces misdiagnosis in clinical settings. Further research is recommended to validate the clinical applicability of SRAR across different types of neuropathies.