Kidney Week

Abstract: TH-PO676

Iron Status and Cause-Specific Mortality in Kidney Transplant Recipients

Session Information

• Anemia and Iron Metabolism
  November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
  Abstract Time: 10:00 AM - 12:00 PM

Category: Anemia and Iron Metabolism

• 200 Anemia and Iron Metabolism

Authors

• Vinke, Joanna Sophia Jacoline, Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Joanna Sophia Jacoline Vinke,

• Kremer, Daan, Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Daan Kremer,

• Knobbe, Tim J., Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Tim J. Knobbe,

• Berger, Stefan P., Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Stefan P. Berger,

• Bakker, Stephan J.L., Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Stephan J.L. Bakker,

• De Borst, Martin H., Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Martin H. De Borst,

• Eisenga, Michele F., Department of Nephrology, University Medical Center Groningen, Groningen, Netherlands

Michele F. Eisenga,

Background

Iron deficiency (ID) is highly prevalent after kidney transplantation. Previously, we showed that ID, independent of anemia, is associated with an increased risk of all-cause mortality in kidney transplant recipients (KTRs). Iron is involved in myriad processes, ranging from cardiomyocyte metabolism to being fuel for bacteria. We further explored the associations of iron status parameters with different cause-specific mortality reasons in KTRs.

Methods

We used data from the prospective Transplantlines Food and Nutrition Study, for which baseline measurements were performed in KTRs that were ≥1 year post-transplantation. Cox regression analyses of recently updated follow-up data were used to assess associations of ferritin, reflecting iron storage, and transferrin saturation (TSAT), reflecting functional iron status, with cause-specific mortality. Analyses were adjusted for age, sex, eGFR, 24-hour urinary protein excretion, time since transplantation, hs-CRP, systolic blood pressure, smoking status and presence of anemia. Anemia was defined as Hb <13 g/dL (M) or <12 g/dL (F).

Results

We included 695 KTRs (age 53±13 years, 57% males, eGFR 52±20 mL/min/1.73 m², ferritin 118 µg/L [IQR 54–222], and TSAT 25±11%). 292 (41%) KTRs had anemia. During 5.9 [IQR 5.3–6.6] years of follow-up, 148 (21%) died: 59 (9%) from cardiovascular causes, 41 (6%) from infections and 25 (4%) from cancer. Tertiles of ferritin were not associated with all-cause mortality or with any of the cause-specific mortality endpoints. A lower TSAT was associated with a higher risk of all-cause mortality [HR 1.26 (95% CI: 1.06–1.50) per 10% decrease, P=0.01] after adjustment for potential confounders. Upon cause-specific analysis, a lower TSAT was not independently associated with a higher risk of death from infection [HR 0.96 (95% CI 0.71–1.29), P=0.77] or cancer [HR 1.10 (95% CI 0.73–1.66), P=0.64], but was associated with a higher risk of cardiovascular mortality [HR 1.39 (95% CI 1.04–1.85), P=0.03].

Conclusion

Lower TSAT was associated with an increased risk of cardiovascular mortality in KTRs, independent of anemia and potential confounders, but not with a higher risk of mortality from other causes. These findings set the stage for prospective studies addressing cardiovascular effects of iron supplementation after kidney transplantation.