What does a Complete Blood Count (CBC) showing microcytic anemia with low Hemoglobin (Hb), low Mean Corpuscular Volume (MCV), low Mean Corpuscular Hemoglobin (MCH), and low Mean Corpuscular Hemoglobin Concentration (MCHC) indicate?

Interpretation of CBC: Microcytic Hypochromic Anemia with Iron Deficiency

This CBC shows classic iron deficiency anemia with microcytosis, hypochromia, and elevated RDW, requiring further workup for the underlying cause and iron supplementation therapy.

Analysis of CBC Values

The CBC shows several abnormal parameters indicating microcytic hypochromic anemia:

• Hemoglobin: 12.0 g/dL (Low) - Below reference range (13.0-17.7 g/dL)
• Hematocrit: 39.0% (Normal) - Within reference range (37.5-51.0%)
• MCV: 78 fL (Low) - Below reference range (79-97 fL), indicating microcytosis
• MCH: 23.9 pg (Low) - Below reference range (26.6-33.0 pg), indicating hypochromia
• MCHC: 30.8 g/dL (Low) - Below reference range (31.5-35.7 g/dL), confirming hypochromia
• RDW: 15.7% (High) - Above reference range (11.6-15.4%), indicating anisocytosis (variable red cell size)

Differential Diagnosis

The combination of low MCV (microcytosis) and high RDW strongly suggests iron deficiency anemia 1, 2. This pattern helps distinguish it from other causes of microcytic anemia:

1. Iron Deficiency Anemia: Low MCV, low MCH, low MCHC, high RDW
2. Thalassemia Trait: Low MCV, normal or low RDW
3. Anemia of Chronic Disease: Can be microcytic but usually normocytic
4. Sideroblastic Anemia: Variable presentation, can be microcytic
5. Lead Poisoning: Microcytic with basophilic stippling

The elevated RDW (>14%) with low MCV is particularly useful in distinguishing iron deficiency from thalassemia trait, as thalassemia typically presents with a normal RDW 1.

Recommended Diagnostic Workup

To confirm iron deficiency and determine its cause:

1. Iron Studies 1, 3:

   • Serum ferritin (<30 μg/L in absence of inflammation, <100 μg/L with inflammation)
   • Serum iron
   • Total iron binding capacity (TIBC)
   • Transferrin saturation (<20% suggests iron deficiency)

2. Source of Blood Loss Investigation:

   • Gastrointestinal evaluation (most common source in adults) 2
   • Menstrual history in females
   • Occult blood testing

3. Consider Additional Testing if iron studies are not conclusive:

   • Hemoglobin electrophoresis (to rule out thalassemia)
   • Reticulocyte count
   • Peripheral blood smear examination

Treatment Approach

1. Iron Supplementation 3, 4:

   • Oral iron: Ferrous sulfate 324 mg (65 mg elemental iron) 2-3 times daily
   • Continue therapy for 2-3 months after hemoglobin normalizes to replenish iron stores
   • Monitor response with repeat CBC after 2-4 weeks

2. Address Underlying Cause:

   • Treat source of blood loss if identified
   • Dietary counseling for increased iron intake

3. Consider Alternative Iron Formulations if intolerant to oral iron:

   • Ferrous gluconate or ferrous fumarate (may have fewer GI side effects)
   • Parenteral iron if severe anemia, malabsorption, or non-compliance

Common Pitfalls to Avoid

1. Failure to investigate the underlying cause of iron deficiency in adults, particularly missing gastrointestinal malignancy 3, 2

2. Misdiagnosing thalassemia trait as iron deficiency - check RDW and consider hemoglobin electrophoresis in patients with persistent microcytosis despite iron therapy 3, 2

3. Stopping iron therapy too soon - iron stores must be replenished after hemoglobin normalizes, requiring 2-3 additional months of treatment 3, 4

4. Relying solely on hemoglobin/hematocrit without evaluating iron status markers, which can miss early iron depletion 5

5. Inappropriate iron supplementation in conditions like thalassemia trait or sideroblastic anemia, where iron overload is a risk 3

This CBC pattern is highly suggestive of iron deficiency anemia, but confirmation with iron studies and investigation of the underlying cause are essential for proper management.