What type of anemia is indicated by microcytic hypochromic anemia lab results?

Microcytic Hypochromic Iron Deficiency Anemia

This is iron deficiency anemia (IDA), confirmed by the combination of microcytic hypochromic indices (MCV 73.5, MCH 24.2) with low ferritin (37 μg/L) and borderline-low hemoglobin (12.4 g/dL). 1, 2

Diagnostic Confirmation

Your laboratory values definitively establish iron deficiency anemia through the following pattern:

• Ferritin 37 μg/L falls below the 45 μg/L threshold that provides optimal sensitivity and specificity for iron deficiency in clinical practice 1, 2
• MCV 73.5 fL demonstrates clear microcytosis (normal >83 fL), which is characteristic of iron deficiency 3, 4
• MCH 24.2 pg shows hypochromia and is actually a more reliable marker than MCV because it's less dependent on storage conditions and the counting machine used 1
• Hemoglobin 12.4 g/dL with hematocrit 37.6% represents mild anemia that warrants investigation when accompanied by confirmed iron deficiency 1

The ferritin level is particularly diagnostic here. While ferritin <15 μg/L indicates absent iron stores with 99% specificity, and <30 μg/L indicates low body iron stores, your value of 37 μg/L still falls below the 45 μg/L cut-off that optimally balances sensitivity and specificity 1, 2. Ferritin >150 μg/L would be needed to exclude absolute iron deficiency, even in the presence of inflammation 1.

Critical Next Steps

You must investigate the source of iron loss, as iron deficiency in adults always requires explanation:

• In men with Hb <110 g/L or non-menstruating women with Hb <100 g/L, fast-track gastrointestinal referral is warranted 1, 2
• Investigation should be considered at any level of anemia with confirmed iron deficiency, especially with more severe degrees, as these patients are more likely to have serious underlying GI pathology 1
• Evaluate for gastrointestinal blood loss through history of melena, hematochezia, or occult bleeding 2
• Consider celiac disease screening if malabsorption is suspected 2

Treatment Protocol

First-line treatment is oral ferrous sulfate 200 mg three times daily for at least three months after correction of anemia to replenish iron stores 2:

• Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 2
• Adding ascorbic acid can enhance iron absorption 2
• A good response is defined as hemoglobin rise ≥10 g/L within 2 weeks, which confirms iron deficiency 2, 5
• Expected hemoglobin increase should be at least 2 g/dL within 4 weeks 2

If oral iron fails, consider intravenous iron if malabsorption is present 2, 6.

Differential Diagnosis Considerations

While iron deficiency is confirmed, you should exclude other causes of microcytosis if the patient doesn't respond appropriately to iron therapy:

• Order hemoglobin electrophoresis if microcytosis persists with normal iron studies, particularly with appropriate ethnic background or if MCV is disproportionately low relative to degree of anemia 1, 2
• Thalassemia trait typically shows elevated red cell count with microcytosis and normal or near-normal RDW 2, 5
• Anemia of chronic disease, sideroblastic anemia, and genetic disorders of iron metabolism must be differentiated to avoid unnecessary iron therapy 2, 7, 8

Monitoring Requirements

• Monitor hemoglobin concentration and red cell indices at three-monthly intervals for one year, then after a further year 2
• Check serum ferritin and transferrin saturation to assess iron store repletion 2
• Provide additional oral iron if hemoglobin or MCV falls below normal 2

Common Pitfalls to Avoid

• Don't assume dietary insufficiency explains the anemia without investigating for blood loss 2
• Ferritin is an acute phase reactant and can be falsely elevated in inflammation, infection, malignancy, or liver disease, potentially masking concurrent iron deficiency 5
• Don't overlook combined deficiencies—iron deficiency can coexist with B12 or folate deficiency 2