What does a CBC showing mild microcytic anemia (low MCH and MCHC), normal RDW, and thrombocytosis (elevated platelet count) indicate?

CBC Interpretation: Microcytic Anemia with Thrombocytosis

The CBC findings of low MCH (25.1 pg) and MCHC (29.7 g/dL) with normal RDW (13.5%) and elevated platelets (504 x10³/uL) most likely indicate iron deficiency anemia, which requires oral iron supplementation with 35-65 mg of elemental iron daily for at least 3 months. 1

Analysis of CBC Parameters

The CBC shows:

• Low MCH (25.1 pg) - Below reference range (26.6-33.0 pg)
• Low MCHC (29.7 g/dL) - Below reference range (31.5-35.7 g/dL)
• Normal RDW (13.5%) - Within reference range (11.7-15.4%)
• High Platelets (504 x10³/uL) - Above reference range (150-450 x10³/uL)

These findings represent a microcytic anemia (low MCH and MCHC) with thrombocytosis (elevated platelet count).

Differential Diagnosis

1. Iron Deficiency Anemia (IDA) - Most likely diagnosis

   • Characterized by low MCH, low MCHC
   • Often associated with thrombocytosis
   • RDW is typically elevated in IDA, but can be normal in early stages 1, 2

2. Thalassemia Trait

   • Also presents with microcytosis
   • Usually has very low MCV (<70 fl)
   • Typically has normal RDW (≤14%)
   • Often has normal or high RBC count 1, 3

3. Anemia of Chronic Disease

   • Can present with microcytosis
   • Usually has normal/slightly elevated RDW
   • Ferritin is typically normal or high 1

Why Iron Deficiency is Most Likely

The combination of microcytosis with thrombocytosis strongly suggests iron deficiency anemia. Reactive thrombocytosis is a common finding in iron deficiency, occurring as a compensatory mechanism. While the normal RDW might suggest thalassemia, early iron deficiency can present with a normal RDW before significant anisocytosis develops 3.

Recommended Management

1. Diagnostic Confirmation:

   • Measure serum ferritin (most specific test for iron deficiency)
   • Check transferrin saturation (TSAT)
   • Consider hemoglobin electrophoresis if thalassemia is suspected 1

2. Treatment:

   • Oral iron supplementation with 35-65 mg of elemental iron daily
   • Options include ferrous sulfate, ferrous fumarate, or ferrous gluconate 1, 4
   • Continue treatment for 3 months after hemoglobin normalizes to replenish iron stores 1

3. Investigation of Underlying Cause:

   • Evaluate for sources of blood loss (gastrointestinal, menstrual)
   • Assess dietary iron intake
   • Consider malabsorption disorders 5

Monitoring and Follow-up

• Repeat CBC in 4-8 weeks to assess response to therapy
• Monitor ferritin levels to ensure replenishment of iron stores
• If no improvement with oral iron, consider:
  • Adherence issues
  • Malabsorption
  • Need for parenteral iron therapy
  • Alternative diagnoses 1

Common Pitfalls to Avoid

1. Inadequate treatment duration - Failing to continue iron therapy for 3 months after anemia correction 1
2. Incomplete evaluation - Attributing iron deficiency to obvious causes (e.g., menstruation) without investigating other potential sources of blood loss 1
3. Misdiagnosis - Confusing iron deficiency with thalassemia trait, which may require genetic testing for confirmation 6, 3
4. Overlooking combined disorders - Iron deficiency can coexist with other conditions like thalassemia, making diagnosis and treatment more complex 3