AIM: Some reports claim that intravenous iron supplements reduce serum phosphate levels in patients with chronic kidney disease (CKD), including those on dialysis. However, whether divalent oral iron supplements influence serum phosphate levels in patients with CKD remains unclear; thus, this study aimed to address this topic. MATERIALS AND METHODS: The study database was derived from the Aichi Cohort Study of Prognosis in Patients Newly Initiated into Dialysis (AICOPP), which is a multicenter, prospective, cohort study. Patients were classified into two groups: those who received iron orally (iron group, n = 255) from pre-dialysis to dialysis initiation and those who did not receive iron supplements (no-iron group, n = 1,261). Moreover, patients were classified into two groups (255 patients in each) by propensity score (PS) matching. We compared serum phosphate level at dialysis initiation and all-cause mortality. Multivariate regression analysis was used to extract factors contributing to serum phosphate level at dialysis initiation through a stepwise method. RESULTS: Serum phosphate levels at dialysis initiation were significantly lower in the iron group (all cohort, 6.0 ± 1.6 vs. 6.4 ± 1.9 mg/dL, p = 0.001; PS-matched cohort, 6.0 ± 1.6 vs. 6.5 ± 1.7 mg/dL, p = 0.001). Multivariate regression analysis revealed that oral iron supplementation was significantly correlated to serum phosphate level (p = 0.023). There were no significant differences in all-cause mortality after dialysis initiation. CONCLUSION: This study showed that oral ferrous citrate or ferrous sulfate use during predialysis was associated with differences in serum phosphate level at dialysis initiation.
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