Low Ankle-Brachial Index in Patients on Hemodialysis Is Associated with Elevated Serum Levels of Spermine Oxidase and C-Reactive Protein

Peripheral arterial disease (PAD) is a major cardiovascular complication of hemodialysis (HD), during which inflammation and oxidative stress contribute to vascular injury. The role of spermine oxidase (SMOX), a polyamine-metabolizing enzyme generating hydrogen peroxide, in PAD is unknown in HD. This cross-sectional study included 142 patients on maintenance HD, including 115 with a normal ankle–brachial index (ABI) (≥0.9) and 27 with a low ABI (<0.9). Patients with a low ABI were older and had lower creatinine and albumin levels, fractional clearance index for urea, and urea reduction ratio but higher levels of glucose, C-reactive protein (CRP), and SMOX; diabetes mellitus was also more prevalent (p < 0.05 for all). In Firth-penalized multivariable logistic regression, SMOX (adjusted odds ratio [aOR] per 1 ng/mL increase, 1.063; 95% confidence interval [CI], 1.018–1.115; p = 0.001) and CRP (aOR per 0.1 mg/dL increase, 1.181; 95% CI, 1.079–1.321; p < 0.001) were independently associated with ABI-defined PAD. Conventional and penalized sensitivity analyses yielded similar estimates. The areas under the curve for SMOX and CRP were 0.790 and 0.804, respectively. SMOX was inversely correlated with bilateral ABI and positively correlated with CRP. SMOX may represent a candidate biomarker associated with ABI-defined PAD in patients undergoing HD, although further validation in larger prospective cohorts is required.