What does it mean if ferritin is low, eosinophil count is low, and iron levels are normal?

Understanding Low Ferritin with Normal Iron and Low Eosinophils

Low ferritin with normal iron levels and low eosinophil count most likely indicates early iron deficiency without anemia, possibly in the context of an inflammatory condition that is suppressing eosinophil production. 1

Iron Status Interpretation

Low Ferritin with Normal Iron

• This pattern suggests early iron depletion where iron stores are being depleted but circulating iron levels remain normal
• Ferritin is the most sensitive marker for iron stores and decreases before changes in serum iron occur 1
• In non-inflammatory conditions:
  • Ferritin <30 μg/L indicates absolute iron deficiency 1
  • This can occur before anemia develops (pre-anemic iron deficiency)

Diagnostic Considerations

• The interpretation of ferritin must consider inflammatory status:

  • In inflammatory conditions, ferritin levels up to 100 μg/L may still represent iron deficiency 1, 2
  • Ferritin is an acute phase reactant that increases during inflammation, potentially masking iron deficiency 2

• Additional testing recommended:

  • Complete blood count with red cell indices
  • Transferrin saturation (TSAT = serum iron ÷ total iron binding capacity × 100)
  • TSAT <16% with ferritin between 30-100 μg/L suggests iron deficiency 2, 1

Low Eosinophil Count (Eosinopenia)

• Low eosinophil count can be associated with:

  • Acute inflammatory response/stress
  • Corticosteroid use
  • Certain infections
  • Autoimmune conditions

• The combination of low eosinophils with low ferritin but normal iron may suggest:

  • An underlying inflammatory condition causing both eosinopenia and elevated ferritin (making ferritin appear higher than it would be without inflammation)
  • This inflammatory state may be masking more severe iron deficiency 2

Clinical Implications

Further Evaluation Needed

• Assess for symptoms of iron deficiency even without anemia:

  • Fatigue
  • Reduced exercise tolerance
  • Difficulty concentrating
  • Restless legs syndrome 3

• Investigate potential causes:

  • Occult blood loss (gastrointestinal, menstrual)
  • Malabsorption (celiac disease, post-bariatric surgery)
  • Inadequate dietary intake
  • Chronic inflammatory conditions 1, 3

• Consider screening for celiac disease, especially if ferritin is low 2, 1

Pitfalls to Avoid

• Don't rely solely on hemoglobin and hematocrit to assess iron status - these decrease only in late-stage iron deficiency 4
• Don't dismiss iron deficiency just because iron levels are normal - ferritin is more sensitive for detecting early iron depletion 1, 4
• Don't use standard ferritin cutoffs in inflammatory states - higher cutoffs (up to 100 μg/L) should be used 2, 1, 5

Management Approach

1. Confirm iron deficiency with additional testing (transferrin saturation)
2. Investigate underlying cause of both low ferritin and low eosinophils
3. Consider oral iron supplementation if iron deficiency is confirmed:
   • Ferrous sulfate 325 mg daily (65 mg elemental iron)
   • Take on empty stomach with vitamin C to enhance absorption
   • Avoid tea, coffee, calcium, and antacids which inhibit absorption 1
4. Monitor response with repeat ferritin and complete blood count in 1-2 months
5. Address any underlying inflammatory condition causing eosinopenia

This combination of findings warrants further investigation to identify the underlying cause and prevent progression to iron deficiency anemia.