C3 and Neurodevelopmental delay: The area under the curve (AUC) of C3 for predicting VC was 0.849 g/L (sensitivity, 79.4%; specificity, 76.7%).<h4>Conclusion</h4>In patients with NDD-CKD, serum complement C3 exhibits a J-shaped relationship with vascular calcification, indicating a complex, non-linear association.