Association of Serum Calcium Levels With Coronary Artery Calcification in Patients at the Initiation of Hemodialysis

INTRODUCTION: The relationship between serum calcium levels at the initiation of hemodialysis and coronary artery calcium score (CACS) remains unclear. This study examined whether albumin-corrected calcium (correctedCa; Payne's formula) and ionized calcium (ionizedCa) measured at dialysis initiation are associated with CACS assessed by screening coronary computed tomography. METHODS: This single-center cross-sectional study included 176 adults who initiated hemodialysis between 2015 and 2023 and underwent coronary computed tomography with CACS measurement within ±30 days. Restricted cubic spline (RCS) logistic regression was used to evaluate the associations of correctedCa and ionizedCa with CACS ≥ 400, adjusting for clinical covariates. Subgroup analyses were performed according to the median serum albumin level. For models in which nonlinearity was not significant, logistic models treating the variable as a linear term were fitted to calculate odds ratios (OR) per 1-standard deviation (SD) increase. FINDINGS: . Higher calcium levels were associated with higher CACS. ionizedCa showed a linear association with CACS ≥ 400 (OR per 1-SD, 1.51; 95% CI, 1.08-2.11). correctedCa also showed a statistically linear association (OR per 1-SD, 1.53; 95% CI, 1.09-2.13), although the RCS curve visually plateaued at higher correctedCa levels. Subgroup analyses revealed that this convex pattern was driven by the low-albumin group. DISCUSSION: Higher calcium at hemodialysis initiation was associated with increased coronary calcification. ionizedCa tended to show a more stable linear relationship with CACS than correctedCa, as correctedCa may overestimate ionizedCa in patients with low albumin. Measurement of ionizedCa at dialysis initiation may help refine vascular calcification risk stratification as patients enter the dialysis period.