What does a CBC indicating microcytic, hypochromic anemia mean?

Interpretation of Microcytic Hypochromic Anemia on CBC

This CBC shows microcytic hypochromic anemia, which most commonly indicates iron deficiency anemia (approximately 80% of cases), though other conditions like thalassemia, anemia of chronic disease, and sideroblastic anemia should be considered in the differential diagnosis. 1

Laboratory Values Analysis

• MCV: 77 fL (low; normal range 79-97 fL)
• MCH: 23.7 pg (low; normal range 26.6-33.0 pg)
• MCHC: 30.6 g/dL (low; normal range 31.5-35.7 g/dL)

These values collectively indicate:

• Microcytosis (small red blood cells)
• Hypochromia (decreased hemoglobin content per cell)

Differential Diagnosis

1. Iron Deficiency Anemia (Most Likely)

• Most common cause of microcytic hypochromic anemia worldwide (~80% of cases) 1
• High-risk groups include infants, toddlers, premenopausal women, pregnant women, and elderly people 1
• Characterized by:
  • Low serum ferritin (<15 μg/L)
  • Low transferrin saturation (<16-20%)
  • Elevated RDW
  • Low serum iron 2, 3

2. Anemia of Chronic Disease

• Second most common cause of microcytic anemia
• Caused by functional iron deficiency (disturbed iron utilization)
• Characterized by:
  • Normal or elevated serum ferritin (>100 μg/L)
  • Low transferrin saturation
  • Normal or slightly elevated RDW
  • Low serum iron 2, 1

3. Thalassemia

• Genetic disorder of hemoglobin synthesis
• Characterized by:
  • Very low MCV (often <70 fL)
  • Normal serum ferritin
  • Normal transferrin saturation
  • Normal RDW 2

4. Sideroblastic Anemia

• Rare genetic disorders affecting heme synthesis
• Can present with microcytic hypochromic anemia
• May be responsive to vitamin B6 (pyridoxine) in some cases 4, 5

Recommended Diagnostic Approach

1. First-line testing:

   • Serum ferritin (most sensitive test for iron deficiency)
   • Transferrin saturation
   • Serum iron and total iron-binding capacity
   • Complete blood count with RDW 2, 3

2. Additional testing based on initial results:

   • If ferritin is normal/high with low iron: inflammatory markers (CRP, ESR)
   • If thalassemia is suspected: hemoglobin electrophoresis
   • If sideroblastic anemia is suspected: bone marrow examination 4, 3

Common Pitfalls to Avoid

• Relying solely on MCV or MCH without confirming iron status 2
• Misinterpreting ferritin levels in inflammatory states (ferritin is an acute phase reactant) 2
• Failing to investigate underlying causes of iron deficiency (e.g., GI bleeding, malabsorption) 2
• Overlooking rare causes like vitamin B6 deficiency in therapy-resistant cases 5
• Not considering concurrent deficiencies that may limit response to therapy 2

Treatment Considerations

Treatment depends on the underlying cause:

• Iron deficiency anemia: Oral iron supplementation (ferrous sulfate 200 mg twice daily) for 3 months after hemoglobin normalizes 2
• Anemia of chronic disease: Treatment of underlying condition 1
• Sideroblastic anemia: Some forms may respond to vitamin B6 (pyridoxine) 50-200 mg daily 4, 5

Monitor response with repeat CBC in 2-4 weeks, with target hemoglobin rise of ≥10 g/L within 2 weeks indicating good response to therapy 2.