Assessing the predictive values of sural/radial amplitude ratio and dorsal sural/radial amplitude ratio in peripheral neuropathy of type 2 diabetes mellitus

Objective: Diabetic peripheral neuropathy (DPN) is a common complication of diabetes; timely detection is critical for preventing severe complications. Traditional nerve conduction studies (NCS) are the gold standard for assessing neuropathy, but traditional NCS cannot detect neuropathy in very early or mild cases. The sural/radial amplitude ratio (SRAR) and dorsal sural/radial amplitude ratio (DSRAR) have emerged as potential markers for identifying early, length-dependent neuropathy in diabetic patients, though standardized cut-off values remain unexplored. This study evaluates the diagnostic effectiveness of the SRAR and DSRAR in identifying diabetic neuropathy (DPN) among individuals with type 2 diabetes mellitus (T2DM). By analyzing sensory nerve conduction parameters of the foot and arm, the study aims to compare the efficacy of these amplitude ratios in distinguishing neuropathic from non-neuropathic individuals. Materials and Methods: A cross-sectional study was conducted among patients with T2DM, classified into neuropathic (VPT > 15) and non-neuropathic (VPT < 15) groups based on vibration perception threshold (VPT). Sural and dorsal sural nerve amplitudes were recorded alongside radial nerve amplitudes, and the SRAR and DSRAR were calculated. A total of 103 participants (mean age: 53.55 ± 10.57 years; mean body mass index: 25.34 ± 4.31 kg/m 2 ) with T2DM (mean duration: 9.28 ± 6.54 years) were included. Diagnostic accuracy, sensitivity, specificity, and predictive values were assessed using receiver operating characteristic analysis and the area under the curve (AUC) was calculated for both SRAR and DSRAR. Results: Sural and dorsal sural nerve amplitudes were significantly lower in the neuropathic group ( P < 0.01). The mean SRAR was 0.72 ± 0.23 in non-neuropathic participants and 0.56 ± 0.25 in those with neuropathy ( P = 0.004). Similarly, DSRAR was markedly reduced in the neuropathic group (0.22 ± 0.03 vs. 0.28 ± 0.02; P = 0.001). At cut-off values of 0.59 (SRAR) and 0.26 (DSRAR), the sensitivity and specificity of DSRAR (83.72% and 86.36%) surpassed those of SRAR (68.97% and 62.16%). Conclusion: Both SRAR and DSRAR demonstrate diagnostic potential for detecting diabetic neuropathy; however, DSRAR exhibits superior sensitivity, specificity, and overall diagnostic accuracy. With its higher predictive values and robust AUC, DSRAR may be a more reliable non-invasive marker for the clinical evaluation of neuropathy in T2DM patients.