ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005

email@asn-online.org

202-640-4660

The Latest on Twitter

Kidney Week

Abstract: TH-PO675

Urinary Iron and Death 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

  • Kremer, Daan, University Medical Center Groningen, Groningen, Groningen, Netherlands
  • Knobbe, Tim J., University Medical Center Groningen, Groningen, Groningen, Netherlands
  • Vinke, Joanna Sophia Jacoline, University Medical Center Groningen, Groningen, Groningen, Netherlands
  • Luersen, Kai, Christian-Albrechts-Universitat zu Kiel Agrar- und Ernahrungswissenschaftliche Fakultat, Kiel, Schleswig-Holstein, Germany
  • Leaf, David E., Brigham and Women's Hospital, Boston, Massachusetts, United States
  • De Borst, Martin H., University Medical Center Groningen, Groningen, Groningen, Netherlands
  • Rimbach, Gerald, Christian-Albrechts-Universitat zu Kiel Agrar- und Ernahrungswissenschaftliche Fakultat, Kiel, Schleswig-Holstein, Germany
  • Bakker, Stephan J.L., University Medical Center Groningen, Groningen, Groningen, Netherlands
  • Eisenga, Michele F., University Medical Center Groningen, Groningen, Groningen, Netherlands
Background

Circulating markers of iron status are associated with adverse outcomes among kidney transplant recipients (KTRs), but limited data are available on urinary iron. Increased urinary iron can result from (i) increased iron delivery to the kidneys, (ii) increased glomerular passage, or (iii) decreased tubular reuptake. We studied associations of urinary iron with these pathways and with clinical outcomes in KTRs.

Methods

We used data from the prospective TxL FN cohort study, which included prevalent KTRs ≥1y after transplantation. Urinary iron concentrations were measured using mass-spectrometry.

Results

We included 693 KTRs (age 53±13y, 43% female, eGFR 45±19 ml/min/1.73m2). Urinary iron concentrations were assessed at a median of 5.4 years post-transplant [IQR, 2.0 to 12.0]. In linear regression, higher urinary iron was associated with lower eGFR (St. β -0.20; P<0.001), and more tubular injury as assessed using urinary and circulating markers (Figure). In contrast, urinary iron was not associated with transferrin saturation, ferritin, and iron after adjustment for age, sex, and eGFR (P>0.05 for all). Prospectively, higher urinary iron was associated with graft failure, but the association was eliminated after adjustment for proteinuria (Table). Higher urinary iron was independently associated with increased mortality (Table).

Conclusion

Higher urinary iron was associated with worse kidney function, more proteinuria, and increased markers of tubular injury, but not with systemic iron status. In addition, higher urinary iron was independently associated with higher mortality risk in KTRs, which warrants further investigation into the potential of urinary iron as a biomarker in KTRs and other populations.