In a 9‑year‑old with hemoglobin 13.2 g/dL, borderline low mean corpuscular volume, normal red cell distribution width, elevated total iron‑binding capacity, normal ferritin, low platelet count/mean platelet volume, and normal C‑reactive protein and erythrocyte sedimentation rate, is the anemia due to beta‑thalassemia trait or iron deficiency, and what is the appropriate work‑up and management?

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Diagnosis: Iron Deficiency Anemia, Not Beta-Thalassemia Trait

This 9-year-old has iron deficiency anemia (IDA), not beta-thalassemia trait (BTT), based on the elevated total iron-binding capacity (TIBC) and normal inflammatory markers, and should receive oral iron supplementation followed by repeat hemoglobin electrophoresis if microcytosis persists after iron repletion.

Diagnostic Reasoning

Why Iron Deficiency is the Primary Diagnosis

  • Elevated TIBC is the key discriminator: Raised TIBC is a specific marker of iron deficiency, as the body attempts to maximize iron transport capacity when stores are depleted 1.

  • Normal ferritin does NOT exclude iron deficiency in children: While ferritin <30 μg/L is diagnostic of iron deficiency in the absence of inflammation 1, normal ferritin levels can occur with true iron deficiency, particularly in children where ferritin cutoffs are less well-established 1. The normal CRP and ESR confirm no inflammatory confounding 1.

  • Borderline low MCV with normal RDW: In pure BTT, the MCV is typically reduced out of proportion to the degree of anemia 1. With hemoglobin of 13.2 g/dL (essentially normal for a 9-year-old per WHO criteria of >11.5 g/dL) 1, a borderline low MCV suggests early iron deficiency rather than BTT 2.

  • Normal RDW argues against isolated IDA but doesn't exclude it: While RDW is typically elevated in IDA and normal in BTT 1, the RDW can be normal in early iron deficiency before significant anisocytosis develops 2. In BTT, RDW is characteristically normal or only mildly elevated 3.

Critical Pitfall: Coexisting Conditions

The most important clinical trap is that IDA and BTT frequently coexist 4. When both conditions are present simultaneously, iron deficiency can mask the typical BTT findings:

  • Iron deficiency lowers HbA2 levels, potentially bringing them into the normal range and obscuring BTT diagnosis 4.
  • The elevated TIBC in this case strongly suggests active iron deficiency that must be corrected first 4.

Appropriate Work-Up Algorithm

Step 1: Confirm Iron Deficiency (Already Done)

  • Elevated TIBC ✓
  • Normal inflammatory markers (CRP, ESR) ✓
  • Consider checking serum iron and transferrin saturation if available—expect low iron and low TSAT (<20%) 1.

Step 2: Initiate Iron Therapy

  • Oral iron supplementation: Provide elemental iron 3-6 mg/kg/day (maximum 100 mg elemental iron daily) 1.
  • Duration: Continue for 20 weeks minimum to replete stores 4.
  • Expected response: Hemoglobin should increase by 1-2 g/dL within 4-8 weeks 1.

Step 3: Reassess After Iron Repletion (Critical Step)

Repeat complete blood count, iron studies, AND hemoglobin electrophoresis at 20 weeks 4:

  • If MCV normalizes and HbA2 remains normal (<3.5%): Diagnosis is isolated IDA 4, 2.
  • If MCV remains low and HbA2 is now elevated (>3.5%): Diagnosis is coexisting IDA + BTT 4.
  • If ferritin normalizes but microcytosis persists with normal HbA2: Consider hemoglobin electrophoresis to exclude thalassemia, as microcytosis can persist despite iron repletion in BTT 1.

Step 4: Identify Source of Iron Loss

In a 9-year-old with confirmed IDA, investigate for:

  • Dietary insufficiency: Most common in children 1.
  • Gastrointestinal blood loss: Less common than adults but must be considered 1.
  • Rapid growth phase: Increased iron demands 1.
  • Menstruation: If post-menarchal female 1.

Management Strategy

Immediate Management

  • Start oral iron therapy now without waiting for hemoglobin electrophoresis 4.
  • Monitor for response at 4-8 weeks with repeat CBC 1.

Definitive Diagnosis

  • Hemoglobin electrophoresis should be deferred until after iron repletion 1, 4. Performing it now may yield falsely normal HbA2 if BTT coexists, leading to missed diagnosis 4.

Long-term Monitoring

  • Recheck ferritin every 3-6 months after correction to detect recurrence 1.
  • Goal ferritin >50 ng/mL in the absence of inflammation 1.

Key Clinical Pearls

  • Never diagnose or exclude thalassemia trait in the presence of iron deficiency—iron deficiency suppresses HbA2 levels 1, 4.
  • Elevated TIBC is highly specific for iron deficiency and overrides normal ferritin in diagnostic decision-making 1.
  • Normal inflammatory markers (CRP, ESR) are essential context—they confirm that ferritin interpretation is not confounded by acute phase reaction 1.
  • The low platelet count and MPV are likely unrelated to the anemia diagnosis and may warrant separate hematologic evaluation if persistent.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Research

Evaluation of microcytosis.

American family physician, 2010

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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