Background: Systemic immune-inflammation index (SII), a novel inflammatory marker, has been demonstrated to be associated with type 2 diabetes mellitus (T2DM) and its vascular complications, however, the relation between SII and diabetic peripheral neuropathy (DPN) has been never reported. We aimed to explore whether SII is associated with DPN in Chinese population.
Methods: A cross-sectional study was conducted among 1460 hospitalized patients with T2DM. SII was calculated as the platelet count × neutrophil count/lymphocyte count, and its possible association with DPN was investigated by correlation and multivariate logistic regression analysis, and subgroup analyses.
Results: Patients with higher SII quartiles had higher vibration perception threshold and prevalence of DPN (all P< 0.01), and SII was independently positively associated with the prevalence of DPN (P< 0.01). Multivariate logistic regression analysis showed that the risk of prevalence of DPN increased progressively across SII quartiles (P for trend < 0.01), and participants in the highest quartile of SII was at a significantly increased risk of prevalent DPN compared to those in the lowest quartile after adjustment for potential confounding factors (odds rate: 1.211, 95% confidence intervals 1.045– 1.404, P< 0.05). Stratified analysis revealed positive associations of SII quartiles with risk of prevalent DPN only in men, people less than 65 years old, with body mass index < 24 kg/m², duration of diabetes > 5 years, hypertension, dyslipidaemia, poor glycaemic control, and estimated glomerular filtration rate < 90 mL/min/1.73 m² (P for trend < 0.01 or P for trend < 0.05). The receiver operating characteristic curve analysis revealed that the optimal cut-off point of SII for predicting DPN was 617.67 in patients with T2DM, with a sensitivity of 45.3% and a specificity of 73%.
Conclusion: The present study showed that higher SII is independently associated with increased risk of DPN, and SII might serve as a new risk biomarker for DPN in Chinese population.

Keywords: systemic immune-inflammation index, diabetic peripheral neuropathy, vibration perception threshold, type 2 diabetes mellitus, Chinese population