Management of Microcytic Hypochromic Anemia with High RDW
Start oral iron supplementation with ferrous sulfate 200 mg three times daily immediately, as the elevated RDW (>14.0%) combined with low MCV strongly indicates iron deficiency anemia rather than thalassemia. 1, 2
Diagnostic Confirmation
Your laboratory pattern—high RBC count with low MCV, low MCH, low MCHC, and elevated RDW—creates a classic signature for iron deficiency anemia:
The elevated RDW (>14.0%) is the key discriminator: When combined with microcytosis, this pattern points to iron deficiency anemia, whereas thalassemia minor typically presents with RDW ≤14.0%. 1, 2
Measure serum ferritin first as the most specific confirmatory test, with levels <30 μg/L indicating low iron stores, though a cutoff of 45 μg/L provides optimal sensitivity and specificity. 1, 2
Check transferrin saturation (TSAT), which is more sensitive for detecting iron deficiency than hemoglobin concentration alone. 1, 2
The high RBC count with microcytosis distinguishes this from anemia of chronic disease, where RBC production is typically suppressed. 3
Treatment Protocol
First-Line Oral Iron Therapy
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 with ferrous sulfate. 1, 2
Expected response: Hemoglobin rise ≥10 g/L (≥1 g/dL) within 2 weeks confirms iron deficiency; expect at least 2 g/dL increase within 4 weeks. 1, 2
When to Consider Intravenous Iron
If no response to oral iron after 4 weeks, consider IV iron (iron sucrose or ferric gluconate) if malabsorption is present, with expected hemoglobin increase of at least 2 g/dL within 4 weeks. 1, 4
Evaluate for genetic disorders of iron metabolism (such as IRIDA/TMPRSS6 defects) if ferritin is low-normal (>20 μg/L) with low TSAT or if there is family history of refractory anemia. 1
Monitoring Strategy
Check hemoglobin and red cell indices at three-monthly intervals for one year, then after a further year. 1, 2
Provide additional oral iron if hemoglobin or MCV falls below normal during follow-up. 1, 2
Monitor serum ferritin and transferrin saturation to assess iron store repletion. 1
Critical Pitfalls to Avoid
Do not assume all microcytic anemia is iron deficiency: If ferritin is normal or elevated (>20 μg/L) despite microcytosis, consider anemia of chronic disease, genetic disorders of iron metabolism, or sideroblastic anemia. 1, 5
Do not overlook combined deficiencies: Iron deficiency can coexist with B12 or folate deficiency, which may mask the typical response to iron therapy. 1, 6
Do not stop iron supplementation when hemoglobin normalizes: Continue for at least three months after correction to replenish iron stores. 1, 2
If RDW were normal or near-normal with microcytosis, you would need to test for thalassemia trait before starting iron therapy, as iron supplementation is ineffective and potentially harmful in thalassemia. 1, 7
Special Considerations for Refractory Cases
Consider pyridoxine (vitamin B6) deficiency if there is history of gastrointestinal surgery or malabsorption, as B6 is necessary for heme biosynthesis and deficiency can cause therapy-resistant microcytic anemia. 6
For X-linked sideroblastic anemia (ALAS2 defects), initiate pyridoxine 50-200 mg daily as initial dose, with lifelong supplementation at 10-100 mg daily if responsive. 1
Evaluate for gastrointestinal blood loss through history of melena, hematochezia, or occult bleeding, and screen for celiac disease if malabsorption is suspected. 1