Supplementary Material for: Calcium‒Phosphorus Metabolism in Chronic Kidney Disease and Its Relationship with Vascular Calcification

Objective: To explore bone metabolism in chronic kidney disease (CKD) and its correlation with nutritional indicators and to identify risk factors for abdominal aortic calcification (AAC).
Methods: This cross-sectional study enrolled 148 adults (>18 years) with CKD stages 3–5 (stage 3: n=13, stage 4: n=15, stage 5: n=120 including dialysis and non-dialysis patients) between May 2018 and May 2021. Participants met strict criteria: confirmed CKD diagnosis per Kidney Disease Outcomes Quality Initiative guidelines, stable nutritional status without malabsorption disorders and no vitamin K antagonist use. Exclusion criteria included acute kidney injury, transplant recipients, malignancies and thyroid/parathyroid disorders. Using convenience sampling, we assessed correlations between nutritional/mineral markers via Pearson's analysis and identified intima–media thickness (IMT)/AAC risk factors through binary logistic regression.
Results: Positive correlations were observed between serum calcium and 25-hydroxyvitamin D (25‐[OH]D), haemoglobin, albumin (Alb), prealbumin (PAlb) and serum magnesium. Negative correlations were found with blood urea nitrogen (BUN), serum creatinine (SCr), the estimated glomerular filtration rate (eGFR), serum phosphorus and intact parathyroid hormone (iPTH). Serum phosphorus was positively correlated with BUN, SCr, uric acid, cystatin C (CysC), calcium–phosphate product (Ca×P), iPTH, PAlb and serum magnesium and negatively correlated with eGFR and 25‐(OH)D. Parathyroid hormone levels were positively correlated with BUN, SCr, CysC, Ca×P, Alb and PAlb and negatively correlated with eGFR and 25‐(OH)D. Logistic regression identified age, sex, and diabetes as independent risk factors for IMT, and age, dialysis vintage and low Alb as risk factors for AAC. Significant differences in AAC were found for sex, dialysis vintage, cholesterol, high-density lipoprotein and serum calcium levels.
Conclusion: Calcium‒phosphorus metabolism plays a role in vascular calcification in CKD, with age, diabetes, dialysis vintage, lipid levels, and low Alb levels contributing to this process.