What laboratory findings indicate anemia of chronic disease?

Laboratory Findings Indicating Anemia of Chronic Disease

In the presence of biochemical or clinical evidence of inflammation, the diagnostic criteria for anemia of chronic disease (ACD) are serum ferritin >100 μg/L and transferrin saturation <20%. 1

Key Laboratory Parameters

Iron Studies

• Serum ferritin:

  • 100 μg/L in the presence of inflammation 1

  • This distinguishes ACD from iron deficiency anemia, where ferritin is typically <30 μg/L in the absence of inflammation 1

• Transferrin saturation:

  • <20% (or <16% as per some guidelines) 1
  • Low transferrin saturation reflects reduced iron availability for erythropoiesis

• Serum iron:

  • Low to normal 1
  • Reflects reduced circulating iron

• Transferrin (TIBC):

  • Low to normal 2
  • Unlike iron deficiency anemia where TIBC is elevated

Red Blood Cell Indices

• Hemoglobin: Reduced (<13 g/dL for men, <12 g/dL for women) 1
• Mean Corpuscular Volume (MCV):
  • Usually normocytic (normal MCV) 1
  • Can sometimes be mildly microcytic 3
• Red Cell Distribution Width (RDW):
  • Elevated in mixed pictures 1
  • Helps distinguish from pure iron deficiency

Inflammatory Markers

• C-reactive protein (CRP): Elevated 1
• Erythrocyte sedimentation rate (ESR): Elevated 1
• Leukocytosis: May be present 1

Mixed Picture Considerations

When serum ferritin is between 30 and 100 μg/L with low transferrin saturation in the presence of inflammation, a combination of true iron deficiency and ACD is likely 1. This mixed picture is common in conditions like inflammatory bowel disease.

Additional Diagnostic Tests

• Soluble transferrin receptor (sTfR):

  • Normal or low in ACD (unlike iron deficiency where it's elevated) 1
  • Helps differentiate between ACD and iron deficiency when available

• Reticulocyte count:

  • Normal to low 1
  • Indicates inadequate bone marrow response to anemia

• Reticulocyte hemoglobin content:

  • Can be useful in monitoring response to therapy 1
  • May help in early detection of functional iron deficiency

Common Pitfalls to Avoid

1. Misinterpreting ferritin levels: Remember that ferritin is an acute phase reactant and can be elevated in inflammatory states despite iron deficiency 1

2. Failing to assess inflammatory status: Always measure inflammatory markers (CRP, ESR) when evaluating anemia, as this affects the interpretation of iron studies 1

3. Overlooking mixed deficiency states: In many chronic diseases, both iron deficiency and ACD can coexist 1

4. Relying on a single parameter: No single test is sufficient for diagnosis; a combination of parameters should be assessed 1

5. Neglecting to consider other causes: Vitamin B12/folate deficiency, drug-induced anemia, and hemolysis should be excluded 1

By systematically evaluating these laboratory parameters in the context of the patient's clinical condition and inflammatory status, ACD can be accurately diagnosed and distinguished from other causes of anemia.