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Iron deficiency (ID) and anemia often coexist. Recent findings showed ID associates with mortality in chronic kidney disease (CKD) patients not requiring dialysis, irrespective of hemoglobin and ferritin levels (Guedes, et al JASN 2021). It is unclear whether ID associates with outcome in patients initiating peritoneal dialysis (PD). This study explores the association between transferrin saturation (TSAT) levels at the start of PD and mortality risks.
We examined data from adults (≥ 18 years) who initiated PD during Dec 2004-Jan 2011 at a national dialysis network in the United States. We included patients that had at least one recorded value for hemoglobin (Hgb), ferritin, and TSAT during the first 180 days of PD. Patients who switched to hemodialysis for ≥ 90 days were excluded from the study. The resulting cohort was subdivided into five categories based on mean TSAT values during the first 180 days: ≤20%, >20%-≤30%, >30%-≤40%, >40%-≤50% and >50%. We plotted Kaplan-Meier survival curves for TSAT groups and assessed mortality risk using Cox proportional hazard models with incremental stepwise adjustments and considered TSAT >20%-≤30% as our reference group.
The cohort included 11,302 patients who started peritoneal dialysis. Overall, 54.4% were male and mean age 55 years old. At baseline (first 180 days of PD), patients had mean Ferritin 444 ng/mL, TSAT 31%, 90% received an ESA dose and 33% received IV iron. There were 41%, 33%, 12%, 10% and 4% of patients with a TSAT of >20%-≤30%, >30%-≤40%, >40%-≤50%, ≤20% and >50%, respectively. Patients with a baseline TSAT ≤20% exhibited the highest crude mortality rate (198.8 deaths per 1,000 patient years). Unadjusted and adjusted Cox models showed consistent results with statistically higher hazard ratios for death among patients with a TSAT ≤20%. Adjusted Cox models showed statistically lower hazard ratios for death in patients with TSAT >30%-≤40% (Table 1, Figure 1 and Figure 2).
We observed that most (41%) patients had a TSAT >20%-≤30%. Majority of patients received ESA (90%), yet a minority of patients received IV iron (33%) during baseline. Patients with a TSAT ≤20% had the highest risk of death even after rigorous adjustments for confounding variables, including hemoglobin, ferritin, ESA use and IV iron use. Patients with TSAT >30%-≤40% exhibited the lowest risk of death. These results are consistent with risks attributable to ID among the non-dialysis CKD population (Guedes, et al JASN 2021). Our results highlight the importance of evaluating ID in the incident PD population, even in the absence of anemia. Additional studies are warranted to confirm these results.