How do you approach a patient with fatigue, pallor, low hemoglobin (Hb) level, and microcytic anemia?

Approach to Microcytic Anemia in a 30-year-old Woman with Fatigue and Pallor

The most appropriate approach for this 30-year-old woman with fatigue, pallor, Hb 9 g/dL, and MCV 70 fL is to order iron studies including ferritin, serum iron, TIBC, and transferrin saturation to confirm iron deficiency anemia, which is the most likely diagnosis. 1

Diagnostic Workup

• Confirm the microcytic anemia with a peripheral blood smear to assess RBC morphology 1
• Order iron studies including:
  • Serum ferritin (most sensitive test for iron deficiency) 1, 2
  • Serum iron 1
  • Total iron binding capacity (TIBC) 1
  • Transferrin saturation 1
• Consider reticulocyte count to assess bone marrow response 1
• If iron studies are inconclusive, consider hemoglobin electrophoresis to evaluate for thalassemia 1, 3

Interpretation of Iron Studies

• Iron deficiency anemia is confirmed by:
  • Low ferritin
  • Low serum iron
  • High TIBC
  • Transferrin saturation < 15% 1
• If ferritin is normal/high with low serum iron, consider anemia of chronic disease 1, 4
• If MCV is particularly low without systemic iron deficiency, consider thalassemia 5, 3

Treatment Approach

• For confirmed iron deficiency anemia, initiate oral iron supplementation with ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily 1, 6
• Do not crush or chew tablets 6
• Monitor response to therapy; if no improvement, consider:
  • Compliance issues
  • Ongoing blood loss
  • Malabsorption
  • Incorrect diagnosis 1

Important Considerations

• In a 30-year-old woman, common causes of iron deficiency include:
  • Menstrual blood loss 2
  • Pregnancy 2
  • Gastrointestinal bleeding 2
• Evaluate for potential sources of blood loss, particularly gastrointestinal bleeding, if anemia is severe or unresponsive to iron therapy 7
• The body has limited capacity to increase iron absorption physiologically, so significant iron loss requires supplementation 2
• If oral iron is not tolerated or ineffective, consider parenteral iron administration 2

Pitfalls to Avoid

• Don't assume iron deficiency without confirming with iron studies, as thalassemia trait can present similarly 1, 3
• Don't overlook potential sources of blood loss, especially gastrointestinal bleeding 2, 7
• Don't fail to consider anemia of chronic disease, which can also present with microcytic anemia 1, 4
• Don't neglect to replete iron stores in addition to correcting the anemia 2