What are the next steps in managing a patient with mild microcytic anemia and thrombocytosis?

Management of Mild Microcytic Anemia with Thrombocytosis

The next step in managing a patient with mild microcytic anemia and thrombocytosis is to obtain iron studies, including serum ferritin, total iron-binding capacity (TIBC), transferrin saturation, and serum iron level, as iron deficiency is the most likely cause of these laboratory findings. 1

Diagnostic Workup

1. Iron Studies (First-line):

   • Serum ferritin (most sensitive test)
   • Total iron-binding capacity (TIBC)
   • Transferrin saturation
   • Serum iron level

2. Additional Testing (based on initial results):

   • If iron deficiency is not confirmed, consider:
     • Hemoglobin electrophoresis (to evaluate for thalassemia trait)
     • Lead levels (if exposure suspected)
     • Inflammatory markers (to assess for anemia of chronic disease)

Interpretation of Laboratory Values

The patient's CBC shows:

• Low MCH (26.4 pg) and MCHC (30.8 g/dL) - consistent with hypochromic anemia
• Normal MCV (85.6 fL) - borderline microcytic
• Elevated platelet count (406,000/uL) - thrombocytosis
• Normal RDW (12.8%) - may help differentiate between causes

This pattern strongly suggests iron deficiency anemia, as it typically presents with:

• Low MCH and MCHC
• Thrombocytosis (reactive)
• Eventually low MCV (though this can be normal early in the process) 1, 2

Management Algorithm

1. If iron deficiency confirmed (low ferritin <15 μg/L):

   • Start oral iron supplementation:
     • Ferrous sulfate 200 mg twice daily (first-line therapy)
     • Consider adding ascorbic acid (250-500 mg twice daily) to enhance absorption
   • Investigate underlying cause of iron deficiency:
     • Evaluate for gastrointestinal blood loss (most common cause in adults)
     • Consider endoscopic evaluation, especially in older adults
     • Assess menstrual blood loss in women of reproductive age 1, 3

2. Monitor response to therapy:

   • Check hemoglobin after 2-4 weeks of iron therapy
   • Expect hemoglobin to rise by approximately 2 g/dL after 3-4 weeks
   • Monitor platelet count - should normalize with iron replacement
   • Continue iron therapy for 3 months after correction of anemia to replenish stores 1

3. If no response to oral iron:

   • Consider IV iron if:
     • Oral iron intolerance
     • Non-response to oral therapy
     • Malabsorption
     • Need for rapid correction 1

Special Considerations

• Thrombocytosis: Reactive thrombocytosis is common in iron deficiency anemia and typically resolves with iron supplementation. The elevated platelet count should not be treated separately but monitored as iron deficiency is corrected 4, 5

• Differential diagnosis: While iron deficiency is most likely, consider:

  • Thalassemia trait (typically has very low MCV, normal ferritin)
  • Anemia of chronic disease (normal/high ferritin, low TIBC)
  • Sideroblastic anemia (rare) 1, 2, 3

• Common pitfalls:

  • Failing to investigate the underlying cause of iron deficiency
  • Stopping iron supplementation too early (before stores are replenished)
  • Misdiagnosing thalassemia trait as iron deficiency
  • Overlooking combined deficiencies (e.g., iron and B12/folate) 1, 3

• Warning signs requiring urgent attention:

  • Severe anemia (Hb <7 g/dL)
  • Active bleeding
  • Symptoms of tissue hypoxia 6

Follow-up should include CBC at 3-month intervals for one year, then after another year to ensure sustained correction and detect recurrence 1.