Abnormal iron status tied to mortality risk in CKD

  • Kidney Int
  • 15 May 2019

  • International Clinical Digest
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Takeaway

  • Abnormal iron balance, particularly functional iron deficiency (FID), is tied to increased mortality in patients with predialysis chronic kidney disease (CKD).

Why this matters

  • Early screening of iron indices can improve cardiovascular risk assessment and treatment of modifiable risk factors.

Study design

  • Veterans Affairs data for 80,067 patients with predialysis CKD (mean age, 72±11 years; mean estimated glomerular filtration rate, 43±11 mL/minute/1.73 m2).
  • Iron groups were based on quartiles of serum transferrin saturation + ferritin concentration: reference (16%-28%; 55-205 ng/mL), low iron (0.4%-16%; 0.4-55 ng/mL), high iron (28%-99.6%; 205-4941 ng/mL), and FID (0.8%-16%; 109-2783 ng/mL).
  • Mortality risks were compared using matching weights based on multinomial propensity score models (matched n=32,489).
  • Funding: Department of Veterans Affairs.

Key results

  • Over a mean 4.0-year follow-up, all-cause mortality was increased in abnormal iron groups vs reference:
    • Low iron: adjusted relative rate (aRR), 1.10; 95% CI, 1.07-1.14.
    • High iron: aRR, 1.09; 95% CI, 1.06-1.13.
    • FID: aRR, 1.21; 95% CI, 1.17-1.25.
  • Similar results observed for nondiabetic vs diabetic subcohorts:
    • Low iron: aRR, 1.09 (95% CI, 1.03-1.14) vs 1.11 (95% CI, 1.07-1.16).
    • High iron: aRR, 1.10 (95% CI, 1.04-1.15) vs 1.09 (95% CI, 1.05-1.14).
    • FID: aRR, 1.23 (95% CI, 1.16-1.30) vs 1.20 (95% CI, 1.15-1.26).

Limitations

  • Observational design.
  • Single measurement.