Is a ferritin level of 48 elevated due to inflammation rather than adequate iron stores?

Ferritin Level of 48: Inflammation vs. Iron Stores

A ferritin level of 48 μg/L is more likely to represent true iron deficiency rather than elevation due to inflammation, as this value falls below the threshold of 100 μg/L that would suggest inflammation-related elevation.

Interpreting Ferritin Levels in Clinical Context

Ferritin is both an iron storage protein and an acute phase reactant that increases during inflammatory states. This dual nature complicates interpretation of ferritin values in clinical practice.

Diagnostic Thresholds

• Non-inflammatory conditions:

  • Ferritin <30 μg/L indicates absolute iron deficiency 1
  • A value of 48 μg/L suggests borderline or early iron deficiency

• Inflammatory conditions:

  • Ferritin up to 100 μg/L may still represent iron deficiency 1, 2
  • Values between 30-100 μg/L with low transferrin saturation (<16%) suggest combined iron deficiency and anemia of chronic disease 3

Assessment of Inflammatory Status

To determine whether a ferritin of 48 μg/L reflects inflammation:

1. Measure inflammatory markers:

   • C-reactive protein (CRP)
   • Erythrocyte sedimentation rate (ESR)
   • Complete blood count for leukocytosis 1

2. Evaluate transferrin saturation (TSAT):

   • TSAT <16% with ferritin between 30-100 μg/L suggests iron deficiency even with inflammation 3
   • TSAT <20% is considered diagnostic for iron deficiency in chronic inflammatory conditions 2

Clinical Implications

A ferritin level of 48 μg/L has different interpretations based on inflammatory status:

• Without inflammation: Represents early or developing iron deficiency
• With inflammation: Likely represents significant iron deficiency despite the seemingly "normal" value

Additional Diagnostic Considerations

• Soluble transferrin receptor (sTfR) measurements can help differentiate between iron deficiency and anemia of inflammation 3
• Reticulocyte hemoglobin content <30 pg can indicate iron-restricted erythropoiesis 1
• In chronic kidney disease, functional iron deficiency should be considered with normal/high ferritin but low TSAT 1, 4

Common Pitfalls in Ferritin Interpretation

1. Assuming normal iron stores with "normal range" ferritin: A ferritin of 48 μg/L may appear within reference range but could still indicate iron deficiency, especially in inflammatory states 5

2. Overlooking inflammation: Inflammation can mask iron deficiency by elevating ferritin levels 2

3. Using inappropriate cutoffs: The traditional cutoff of <30 μg/L is too low for patients with inflammatory conditions 1, 2

4. Relying solely on ferritin: Always interpret ferritin in conjunction with TSAT and inflammatory markers 3, 1

In conclusion, a ferritin level of 48 μg/L should prompt further investigation of iron status, particularly assessment of inflammatory markers and transferrin saturation, as this value likely represents true iron deficiency rather than inflammation-related elevation.