What is the next step for a patient with severe microcytic anemia (low Mean Corpuscular Volume (MCV)) and a hemoglobin level indicating severe anemia?

Blood Transfusion is the Immediate Next Step

For a patient with severe microcytic anemia (hemoglobin 6.2 g/dL) presenting with symptomatic pallor and fatigue, blood transfusion must be performed immediately, followed by oral iron supplementation once stabilized. 1

Rationale for Immediate Transfusion

• Packed red cell transfusions are indicated when hemoglobin decreases below 7.5 g/dL with clinical symptoms, which this patient clearly meets with pallor, fatigue, and hemoglobin of 6.2 g/dL 1
• The American College of Physicians explicitly recommends blood transfusion as the immediate next step for patients with severe anemia at this hemoglobin level, followed by oral iron supplementation once stabilized 1
• Transfuse 2-3 units of packed red blood cells to address the acute anemia while avoiding complications from volume overload 1
• Each 400 mL unit should increase hemoglobin by approximately 1.5 g/dL 1
• This approach is especially critical if the patient has comorbidities, older age, or ischemic heart disease 1

Critical Pitfall to Avoid

• Do not delay transfusion to "work up" the anemia first—hemoglobin of 6.2 g/dL with symptoms requires immediate correction of oxygen-carrying capacity 1
• Do not start with oral iron alone in severe anemia (Hb <7.5 g/dL), as this patient needs rapid correction rather than the slow response that oral iron provides 1

Post-Transfusion Management

After stabilizing the patient with transfusion, the diagnostic workup and treatment should proceed as follows:

Diagnostic Testing

• Serum ferritin is the most specific test for iron deficiency, with levels <30 μg/L indicating low iron stores, though a cutoff of 45 μg/L provides optimal sensitivity and specificity 1, 2
• Transferrin saturation (TSAT) is more sensitive for detecting iron deficiency than hemoglobin alone 1, 2
• Red cell distribution width (RDW): elevated RDW (>14.0%) with low MCV strongly suggests iron deficiency anemia rather than thalassemia trait 1, 2
• Complete blood count with reticulocyte count, CRP, and peripheral smear should be obtained 1

Iron Supplementation Protocol

• Start ferrous sulfate 200 mg (65 mg elemental iron) three times daily for at least three months after correction of anemia to replenish iron stores 1, 2
• Add ascorbic acid (vitamin C) to enhance iron absorption 1, 2
• Alternative formulations include ferrous gluconate or ferrous fumarate if gastrointestinal side effects occur 1, 2
• A good response is defined as hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks, confirming iron deficiency 1, 2

Monitoring Strategy

• Monitor hemoglobin concentration and red cell indices at three-monthly intervals for one year, then after a further year 1, 2
• Expect hemoglobin increase of at least 2 g/dL within 4 weeks of starting oral iron 2
• Provide additional oral iron if hemoglobin or MCV falls below normal 1, 2

When Bone Marrow Biopsy is NOT Indicated

• Bone marrow biopsy is not indicated as a next step in straightforward microcytic anemia with severe symptoms—reserve this for refractory cases after failed iron therapy or when the diagnosis remains unclear 1
• The absence of iron stores in bone marrow remains the most definitive test for differentiating iron deficiency from other microcytic states, but measurement of serum ferritin and transferrin saturation may obviate proceeding to bone marrow evaluation 3

Additional Considerations

• Do not assume all microcytic anemia is iron deficiency: if ferritin is normal or elevated (>20 μg/L) despite microcytosis, consider genetic disorders of iron metabolism or anemia of chronic disease 1, 2
• Do not overlook combined deficiencies, as iron deficiency can coexist with B12 or folate deficiency 1, 2
• For patients who fail to respond to oral iron therapy, consider intravenous iron if there is malabsorption, with expected hemoglobin increase of at least 2 g/dL within 4 weeks 2