Laboratory Values in Anemia of Chronic Disease
In anemia of chronic disease (ACD), the typical laboratory profile shows normal-to-high serum ferritin (>100 μg/L), low transferrin saturation (<20%), low serum iron, and normal-to-elevated total iron binding capacity (TIBC). 1
Key Laboratory Parameters
Complete Blood Count
- Hemoglobin: Typically mild to moderate reduction (usually not below 8 g/dL)
- Hematocrit: Proportionally decreased
- Red Blood Cell Morphology: Normocytic and normochromic (MCV 80-100 fL)
- In some cases (21%), may be microcytic with MCV <80 fL 2
- Reticulocyte Count: Decreased or inappropriately normal for the degree of anemia 3
Iron Studies
- Serum Ferritin: Normal to elevated (>100 μg/L) 1
- This distinguishes ACD from iron deficiency anemia where ferritin is <30 μg/L
- Serum Iron: Low (<60 μg/dL) 2
- Total Iron Binding Capacity (TIBC): Normal to decreased (unlike iron deficiency where TIBC is elevated) 4
- Transferrin Saturation: Low (<20%) 1
- Soluble Transferrin Receptor (sTfR): Normal (elevated in iron deficiency) 5
Inflammatory Markers
- C-Reactive Protein (CRP): Often elevated
- Erythrocyte Sedimentation Rate (ESR): Often elevated
- Interleukin-6 (IL-6): May be elevated 6
- Hepcidin: Elevated (key mediator in ACD) 3
Mixed Anemia (ACD + Iron Deficiency)
Many patients have a combination of ACD and true iron deficiency, which presents diagnostic challenges. In these cases:
- Serum Ferritin: 30-100 μg/L suggests combined ACD and iron deficiency 1
- Transferrin Saturation: <20% 1
- sTfR/log Ferritin Ratio: Elevated (more sensitive for detecting combined state) 5
Distinguishing Features from Iron Deficiency Anemia
| Parameter | Anemia of Chronic Disease | Iron Deficiency Anemia |
|---|---|---|
| Ferritin | Normal to high (>100 μg/L) | Low (<30 μg/L) |
| Serum Iron | Low | Low |
| TIBC | Normal to low | High |
| Transferrin Saturation | Low (<20%) | Low (<16%) |
| MCV | Usually normal | Low (microcytic) |
| RDW | Normal to slightly elevated | Elevated |
| Hepcidin | Elevated | Low |
Clinical Considerations
- The severity of ACD generally correlates with the severity of the underlying disease 3
- In chronic kidney disease (CKD), functional iron deficiency is common even with normal or elevated ferritin levels 7
- Ferritin is an acute phase reactant and may be elevated in inflammatory states regardless of iron status 1
- When evaluating patients with suspected ACD, always consider the possibility of concurrent true iron deficiency, especially in patients with chronic blood loss or malnutrition 4
Common Pitfalls
- Relying solely on ferritin levels without considering inflammatory status can lead to misdiagnosis
- Failing to recognize that up to 20% of ACD cases may present with microcytosis 2
- Not considering combined ACD and iron deficiency when ferritin is between 30-100 μg/L 1
- Overlooking the need to investigate the underlying cause of ACD, which may include infections, inflammatory disorders, malignancies, or chronic kidney disease 3, 2
By understanding these laboratory patterns, clinicians can better diagnose anemia of chronic disease and distinguish it from other common anemias, leading to more appropriate management strategies.