Which serum iron study results are characteristic of transfusion-induced iron overload?

Updated: May 07, 2021
  • Author: Geneva E Guarin, MD, MBA; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

Serum ferritin has been extensively used as an easily accessible serum marker for transfusion-induced iron overload. The ferritin level that has been used as a cutoff point for iron toxicity has varied in studies from 1000 ng/mL to 3000 ng/mL. [44, 45] The major drawbacks of ferritin are a lack of specificity and interpatient variability. [45] Inflammation, disseminated malignancy, and chronic diseases can also cause large amounts of ferritin to be released in the circulation, making a single elevated reading unreliable. [46]

Low serum ferritin levels may be misleading by providing a false sense of security when patients are at risk of end-organ damage such as cardiomyopathy. [47] Ferritin has also been shown to have a prognostic value. In one study of β-thalassemia major, for patients in whom more than 67% of ferritin measurements exceeded 2500 ng/mL, the estimated disease-free survival was 38% after 10 years of therapy and 18% after 15 years. [25]

Serum iron is increased in cases of iron overload and the total iron-binding capacity (TIBC) is decreased. The relationship between serum iron and total body iron is nonlinear, and the results are dependent on the method used. [48]

Transferrin saturation can be easily measured and is a surrogate marker for NTBI, although this is far from perfect. [49] A transferrin saturation above 50% is suggestive of a high iron load, but this is a dynamic number and may vary with inflammation.

NTBI and LPI are very specific for iron overload and have promising value as monitoring parameters for clinical response to chelation therapy. [50] However, the lack of a standardized assay and limited data for general use for transfusion-induced iron overload makes it necessary to further investigate the use of NTBI and LPI.

Hepcidin measurement in serum and urine have been performed using mass spectrometry, and this may be a feasible marker in the future. [51]

The patient's complete blood cell (CBC) count should be monitored for the hemoglobin/hematocrit to maintain a high threshold for transfusion. Liver function tests, especially alanine aminotransferase (ALT) and aspartate aminotransferase (AST), should be monitored. In patients who develop diabetes mellitus, the usual parameters, such as hemoglobin A1C (HbA1C) and glucose, should be monitored.


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