When should I repeat a complete blood count in a 50‑year‑old woman with iron‑deficiency anemia and neutrophilia?

Timing for Repeat CBC in Iron-Deficiency Anemia and Neutrophilia

For iron-deficiency anemia, recheck CBC and iron studies 3 months after starting oral iron therapy; for neutrophilia, repeat CBC in 2–4 weeks to determine if it resolves with iron repletion, as iron deficiency itself can cause neutropenia that paradoxically may appear as reactive neutrophilia during acute correction. 1, 2, 3

Monitoring Schedule for Iron-Deficiency Anemia

Initial Assessment After Starting Oral Iron

• Recheck CBC at 3 months after initiating oral iron supplementation to assess hemoglobin response and confirm iron store replenishment 1, 2
• Simultaneously measure ferritin and transferrin saturation (TSAT) at this 3-month checkpoint to document adequate iron repletion 2
• If hemoglobin has not increased by ≥1 g/dL after 8 weeks of adequate oral therapy, consider switching to intravenous iron 2

Long-Term Surveillance After Correction

• Once hemoglobin normalizes, monitor CBC every 3 months for the first year to detect recurrent anemia 1, 2
• After the first year, recheck at 6 months, 12 months, and 24 months from completion of therapy 1
• In patients with inflammatory bowel disease in remission, extend monitoring to every 6–12 months 1

Special Timing Considerations

• Do not recheck iron studies within 4 weeks of intravenous iron administration, as ferritin will be falsely elevated and unreliable 2, 4
• The optimal window for reassessing iron parameters after IV iron is 4–8 weeks after the last infusion 2, 4

Monitoring Schedule for Neutrophilia

Initial Repeat CBC

• Repeat CBC in 2–4 weeks to determine whether the neutrophilia persists or resolves with iron therapy 3, 5
• Iron deficiency can paradoxically affect white blood cell counts, including causing neutropenia that may normalize with iron repletion 3, 5

Interpretation of Neutrophilia in Iron Deficiency

• Neutrophilia in the setting of iron-deficiency anemia may represent:
  • Reactive leukocytosis from underlying inflammation or infection
  • Bone marrow response to correction of iron deficiency 5
  • Unrelated pathology requiring separate investigation if it persists beyond 4 weeks

When to Pursue Further Workup

• If neutrophilia persists after 4 weeks despite correction of anemia, consider alternative causes (infection, inflammation, malignancy, medications) 1
• If two or more cell lines are abnormal (e.g., neutrophilia plus thrombocytosis or thrombocytopenia), consult hematology for possible primary bone marrow disorder 1

Algorithmic Approach to Monitoring

Week 0 (Baseline)

• Obtain CBC with differential, reticulocyte count, ferritin, TSAT, and CRP 1
• Document hemoglobin, MCV, and absolute neutrophil count 1

Week 2–4

• Repeat CBC to assess early hemoglobin response and neutrophil trend 2, 3
• If hemoglobin has not increased or neutrophilia worsens, consider non-iron causes 2

Week 8–12 (3 Months)

• Repeat CBC, ferritin, and TSAT to confirm adequate response 1, 2
• Target hemoglobin normalization and ferritin ≥30 μg/L (≥100 μg/L if inflammation present) 1
• If neutrophilia has resolved, no further white cell monitoring needed unless symptoms develop 3

Months 6,12,24

• Repeat CBC to detect recurrent anemia 1, 2
• If anemia recurs, reinitiate full workup including ferritin, TSAT, and evaluation for ongoing blood loss 1

Common Pitfalls and Caveats

Premature Iron Study Assessment

• Measuring ferritin too soon after IV iron (within 4 weeks) yields falsely elevated results that do not reflect true iron stores 2, 4
• This leads to undertreatment and recurrent anemia 2

Inadequate Duration of Therapy

• Stopping oral iron as soon as hemoglobin normalizes without replenishing stores (requires at least 3 months of therapy) results in rapid recurrence 1, 2
• More than 50% of patients develop recurrent anemia within 1 year if iron stores are not fully repleted 1

Misinterpreting Ferritin in Inflammation

• Ferritin is an acute-phase reactant; a "normal" ferritin of 50 μg/L may still represent iron deficiency if CRP is elevated 1
• In the presence of inflammation, ferritin up to 100 μg/L may still indicate iron deficiency 1

Overlooking Persistent Neutrophilia

• If neutrophilia persists beyond 4 weeks despite anemia correction, it requires separate investigation and is not attributable to iron deficiency 3, 5
• Failure to pursue this may delay diagnosis of infection, malignancy, or myeloproliferative disorder 1

Ignoring Recurrent Anemia

• Recurrent anemia after initial correction suggests ongoing blood loss, malabsorption, or undiagnosed pathology (e.g., gastrointestinal malignancy, renal cell carcinoma) 1
• Repeat bidirectional endoscopy if original studies are >2 years old or if anemia recurs despite adequate iron therapy 1