What is the management for a patient with microcytic anemia?

Management of Microcytic Anemia (Hb 10.5 g/dL, MCV 84.7 fL)

The first priority is to confirm iron deficiency anemia with serum ferritin testing (<15 μg/L confirms absent iron stores, <30 μg/L indicates low body iron stores), then initiate oral iron supplementation with ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily on an empty stomach with vitamin C, while simultaneously investigating the underlying cause of blood loss. 1, 2, 3

Diagnostic Confirmation

Order iron studies immediately:

• Serum ferritin is the most specific single test for iron deficiency, with <15 μg/L indicating absent iron stores and <30 μg/L indicating low body iron stores 2, 3
• In the presence of inflammation, ferritin up to 100 μg/L may still be consistent with iron deficiency 3
• Add serum iron, total iron binding capacity (TIBC), and transferrin saturation (TSAT <16% suggests iron deficiency) 1, 3
• The combination of low hemoglobin (10.5 g/dL), low MCV (84.7 fL), low MCH (26.9 pg), and low MCHC (31.7 g/dL) strongly suggests iron deficiency anemia 1, 3

If iron studies are normal or equivocal:

• Order hemoglobin electrophoresis to evaluate for thalassemia trait 3
• Consider anemia of chronic disease if low iron, low TIBC, and normal/high ferritin are present 3
• In patients with unexplained microcytic anemia despite adequate iron supplementation, consider genetic disorders of iron metabolism or heme synthesis 4, 2

Immediate Treatment Initiation

Start oral iron therapy:

• Ferrous sulfate 325 mg (65 mg elemental iron) 1-3 times daily is first-line therapy 1, 2
• Take on an empty stomach with vitamin C (ascorbic acid) to enhance absorption 1, 2
• Alternative formulations include ferrous gluconate or ferrous fumarate if ferrous sulfate is not tolerated 2
• A good response is defined as hemoglobin rise ≥10 g/L within 2 weeks, which confirms iron deficiency 2

Monitor for treatment response:

• If no response to oral iron after 4-8 weeks, reassess compliance and consider gastrointestinal side effects 1
• Consider intravenous iron if malabsorption is present or oral iron fails 2
• Continue oral iron for at least 3 months after correction of anemia to replete iron stores 2

Investigation of Underlying Cause

The source of iron loss must be identified:

• In menstruating women, evaluate menstrual blood loss patterns 2
• In men and post-menopausal women, gastrointestinal blood loss is the most common cause and requires upper and lower gastrointestinal endoscopy 2, 3, 5
• Evaluate for poor dietary intake, malabsorption disorders (celiac disease, H. pylori infection, autoimmune atrophic gastritis), and NSAID use 4, 2
• In older adults, endoscopy is warranted to evaluate for gastrointestinal malignancy 5

Follow-up and Monitoring

Structured monitoring protocol:

• Monitor hemoglobin concentration and red cell indices at 3-monthly intervals for one year, then after a further year 2
• Provide additional oral iron if hemoglobin or MCV falls below normal 2
• Reticulocyte count may help assess bone marrow response to iron therapy 1
• For patients receiving iron therapy, monitor for iron overload, particularly if genetic disorders are suspected 2

Critical Pitfalls to Avoid

Do not overlook these key considerations:

• Avoid repeated unnecessary trials of iron therapy without confirming iron deficiency with ferritin testing 6
• Do not miss combined deficiencies (iron deficiency coexisting with B12 or folate deficiency) 2
• In patients with refractory microcytic anemia despite adequate iron supplementation, genetic testing should be considered 4, 2
• Unrecognized tissue iron loading in genetic anemias (such as sideroblastic anemias) can lead to severe morbidity and mortality 4
• Exclude common causes first: iron deficiency, severe anemia of chronic disease, thalassemias, and hemoglobinopathies before pursuing rare genetic disorders 4