Utility of Blood Biomarkers to Predict Marrow Iron Stores in Children

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Abstract
Key Points: Serum ferritin was the strongest independent correlate of greater marrow iron stores in children with kidney failure supported by dialysis. Compared with current clinical guideline-based cutoffs for iron deficiency, ferritin outperforms these cut points for stainable marrow iron stores. Background: Iron deficiency is common in children with kidney failure, but current guidelines are based on biomarkers of iron stores that may be influenced by inflammation. This is the first study that examined which serum iron indices were associated with stainable marrow iron stores (the gold standard) in this population with kidney failure who underwent bone biopsies. Methods: This cross-sectional study enrolled 71 clinically stable children and young adults receiving dialysis who underwent bone biopsy for CKD-mineral bone disorder between 2007 and 2011. Bone biopsies were stained with Perls Prussian blue and independently interpreted by a pathologist blinded to participants' iron parameters and clinical status. Marrow staining was scored absent versus present to facilitate receiver operator curve (ROC) analysis. In ROC analysis, the ability of serum ferritin to detect stainable marrow iron stores was compared with that of transferrin saturation (TSAT), serum hepcidin, and clinical guideline-based iron deficiency cutoffs for serum iron, TSAT, and their combinations. Results: The mean age was 17.2±4.4 years (range 2–28), and 30% of patients were female. Median dialysis vintage was 1.2 (interquartile range, 0.7–2.0) years, and 56% were supported by peritoneal dialysis. Mean hemoglobin was 12.4±1.7 g/dl, and 35% were receiving iron supplementation at the time of biopsy. On the basis of the gold standard of depleted marrow iron stores, 46.5% of patients were iron deficient. As an indicator of marrow iron staining, serum ferritin provided a larger area under the ROC curve than serum hepcidin, TSAT, or clinical guideline-based evaluation of TSAT+ferritin. Conclusions: In this cohort of children and young adults with kidney failure, serum ferritin provided the best indication of stainable marrow iron stores, followed by TSAT. Podcast: This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2024_08_01_CJASNJuly197812024.mp3
Funding Information
  • National Institute of Diabetes and Digestive and Kidney Diseases (K24DK110427)
  • National Institute of Diabetes and Digestive and Kidney Diseases (UO1DK122013)
  • U.S. Department of Veterans Affairs (CX002195)
  • National Institute of Diabetes and Digestive and Kidney Diseases (K24DK110427)
  • National Institute of Diabetes and Digestive and Kidney Diseases (UO1DK122013)
  • U.S. Department of Veterans Affairs (CX002195)

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