Diagnosis and Management of Microcytic Hypochromic Anemia with Elevated RDW and Thrombocytosis
This presentation is most consistent with iron deficiency anemia, and you should initiate oral ferrous sulfate 200 mg three times daily for at least three months after hemoglobin correction while simultaneously investigating the underlying cause of iron loss. 1
Diagnostic Interpretation
The combination of laboratory findings strongly points toward iron deficiency anemia:
Low MCV combined with elevated RDW (>14.0%) is highly specific for iron deficiency anemia, distinguishing it from thalassemia minor which typically presents with low MCV but normal RDW (≤14.0%). 1, 2
The thrombocytosis (elevated platelet count) is a reactive phenomenon commonly seen in iron deficiency anemia and supports this diagnosis. 1
Serum ferritin is the single most useful diagnostic test, with levels <30 μg/L confirming iron deficiency in the absence of inflammation, though a cut-off of 45 μg/L provides optimal sensitivity and specificity in practice. 1, 3
If ferritin is falsely elevated due to inflammation, add transferrin saturation to the workup, as this is more sensitive than hemoglobin concentration alone for detecting iron deficiency. 1
Immediate Treatment Protocol
First-line therapy consists of:
Ferrous sulfate 200 mg orally three times daily for at least three months after anemia correction to replenish iron stores. 1, 2
Add ascorbic acid (vitamin C) to enhance iron absorption. 1, 2
Alternative formulations (ferrous gluconate or ferrous fumarate) can be used if ferrous sulfate is not tolerated. 1
Expect hemoglobin to rise ≥10 g/L within 2 weeks if iron deficiency is the cause; this response confirms the diagnosis. 1
Mandatory Investigation of Underlying Cause
You must identify and address the source of iron loss:
In men and post-menopausal women, gastrointestinal blood loss is the most common cause, and gastrointestinal malignancy must be excluded. 2, 3
Men with Hb <110 g/L or non-menstruating women with Hb <100 g/L warrant fast-track GI referral. 1
In pre-menopausal women, heavy menstrual bleeding is the most common cause. 1
Other causes include malabsorption (consider celiac disease screening), dietary inadequacy, previous gastrectomy, and NSAID use. 1, 3
Monitoring Strategy
Check hemoglobin and red cell indices at three-month intervals for one year, then annually. 2, 3
Provide additional oral iron if hemoglobin or MCV falls below normal during follow-up. 1
When Treatment Fails
If the patient fails to respond within 2-4 weeks, consider:
Non-compliance with therapy (most common reason for treatment failure). 1
Ongoing blood loss exceeding oral replacement capacity - switch to intravenous iron. 1, 2
Malabsorption - intravenous iron is required, with expected hemoglobin increase of at least 2 g/dL within 4 weeks. 1, 2
Rare genetic disorders such as IRIDA (iron-refractory iron deficiency anemia), which requires intravenous iron as oral iron is typically ineffective. 1
Critical Differential Diagnosis Considerations
While iron deficiency is most likely, do not assume all microcytic anemia is iron deficiency:
Thalassemia trait presents with low MCV but typically normal or only mildly elevated RDW (≤14.0%), extreme microcytosis (MCV <70), and MCV disproportionately low relative to degree of anemia. 1, 2
Anemia of chronic disease shows low iron with low TIBC and normal/high ferritin, distinguishing it from iron deficiency. 2, 3
Order hemoglobin electrophoresis if microcytosis persists with normal iron studies, appropriate ethnic background, or MCV disproportionately low relative to anemia. 1
Hematology Referral Indications
Refer to hematology if: