What are the next steps in managing a patient with mild microcytic hypochromic anemia and abnormal CBC results?

Management of Mild Microcytic Hypochromic Anemia with Elevated RDW

Start oral iron supplementation with ferrous sulfate 200 mg three times daily immediately, and simultaneously investigate the underlying cause of iron deficiency. 1, 2

Immediate Diagnostic Workup

Your CBC shows classic iron deficiency anemia features:

• Low hemoglobin (12.5 g/dL), low MCH (26.3 pg), and low MCHC (30.3 g/dL) indicate hypochromic microcytic anemia 3
• Elevated RDW (16.8%) with low-normal MCV (87 fL) strongly suggests iron deficiency rather than thalassemia minor, which typically presents with RDW ≤14.0% 1, 2

Essential Iron Studies Required Now:

• Serum ferritin (most specific test; <30 μg/L indicates low iron stores, though <45 μg/L is the optimal clinical cut-off) 1, 2
• Transferrin saturation (TSAT) (more sensitive than hemoglobin alone; <15% suggests absolute iron deficiency) 3, 1
• Total iron binding capacity (TIBC) 3

Investigation for Blood Loss

In any patient with iron deficiency, assume gastrointestinal blood loss until proven otherwise. 2

Mandatory Screening:

• Stool guaiac test for occult blood to detect GI bleeding 3
• Detailed menstrual history if female (most common cause in premenopausal women) 2, 4
• Dietary assessment for inadequate iron intake 2
• Medication review for NSAID use (can cause GI bleeding) 2

Consider GI Endoscopy If:

• Positive stool guaiac 3
• Male patient or postmenopausal female (GI blood loss most common) 2
• Severe anemia or failure to respond to iron therapy 2

Treatment Protocol

First-Line Oral Iron Therapy:

Ferrous sulfate 200 mg (65 mg elemental iron) three times daily, taken separately from meals 1, 2, 5

• Continue for at least 3 months after hemoglobin normalizes to replenish iron stores 1, 2
• Alternative formulations (ferrous gluconate or ferrous fumarate) if ferrous sulfate not tolerated 1, 2
• Add ascorbic acid (vitamin C) to enhance absorption 2

Expected Response:

• Hemoglobin should rise ≥10 g/L (≥1 g/dL) within 2 weeks 1, 2
• If no response after 2-4 weeks, consider: 1, 2
  • Non-compliance or malabsorption
  • Ongoing blood loss exceeding replacement
  • Incorrect diagnosis (genetic disorders, vitamin B6 deficiency)
  • Need for IV iron therapy

Monitoring Schedule

• Recheck CBC at 2 weeks to confirm response to therapy 1, 2
• Monitor hemoglobin and red cell indices every 3 months for 1 year, then annually 1, 2
• Provide additional oral iron if hemoglobin or MCV falls below normal 1, 2

Red Flags Requiring Further Investigation

Consider Genetic Disorders or Alternative Diagnoses If:

• Failure to respond to adequate oral iron therapy after 4 weeks 1, 2
• Family history of microcytic anemia 2
• Normal or elevated ferritin with microcytic anemia (suggests anemia of chronic disease or genetic disorder) 1, 2
• Persistent microcytosis despite iron repletion (consider thalassemia trait) 3, 2

Rare Causes to Consider:

• Vitamin B6 (pyridoxine) deficiency in patients with malabsorption or post-GI surgery (treat with pyridoxine 50-200 mg daily) 1, 6
• Genetic disorders of iron metabolism (SLC11A2, TMPRSS6 defects) if refractory to oral iron 1, 2, 7
• Sideroblastic anemia (may respond to pyridoxine) 1, 7

Intravenous Iron Indications

Switch to IV iron if: 1, 2

• Documented malabsorption
• True intolerance to all oral formulations
• Blood losses exceeding maximal oral replacement capacity
• Expected hemoglobin increase ≥2 g/dL within 4 weeks of IV iron 1

Critical Pitfalls to Avoid

• Do not overlook combined deficiencies (iron with B12 or folate deficiency can coexist) 2
• Do not stop iron therapy when hemoglobin normalizes—continue for 3 months to replenish stores 1, 2
• Do not assume dietary insufficiency alone—always search for blood loss 3, 4
• Monitor for iron overload in patients requiring long-term therapy or multiple transfusions 1, 2