Can you interpret this CBC with differential showing hemoglobin 9.4 g/dL, hematocrit 30.6 %, MCV 70.3 fL, MCH 21.6 %, MCHC 30.7 g/dL, RDW 16.5 %, platelet count 219 K/µL, MPV 10.6 fL, and a normal white‑cell differential?

Microcytic Hypochromic Anemia with Iron Deficiency

This CBC demonstrates microcytic hypochromic anemia (MCV 70.3 fL, MCH 21.6 pg, MCHC 30.7 g/dL, Hgb 9.4 g/dL) with elevated RDW (16.5%), most consistent with iron deficiency anemia, and requires immediate iron studies (serum ferritin and transferrin saturation) followed by investigation for a source of blood loss, particularly gastrointestinal bleeding.

Key Abnormalities

The critical findings are:

• Hemoglobin 9.4 g/dL (low, defines anemia)
• Hematocrit 30.6% (low)
• MCV 70.3 fL (markedly low - microcytic)
• MCH 21.6 pg (markedly low - hypochromic)
• MCHC 30.7 g/dL (low)
• RDW 16.5% (elevated - indicates heterogeneous red cell population)
• MPV 10.6 fL (mildly elevated)

The white blood cell differential and platelet count are completely normal, indicating this is an isolated red cell problem.

Interpretation and Differential Diagnosis

Primary Diagnosis: Iron Deficiency Anemia

The combination of microcytosis (MCV <80 fL), hypochromia (MCH <26 pg, MCHC <31 g/dL), and elevated RDW strongly suggests iron deficiency 1. The low MCV typically indicates deficiencies of iron, folic acid, vitamin B12, or inherited disorders of hemoglobin synthesis 1.

Alternative Considerations

Thalassemia trait must be considered in the differential. However, several features favor iron deficiency over thalassemia:

• The elevated RDW (16.5%) is more typical of iron deficiency; thalassemia trait usually presents with normal or only mildly elevated RDW
• The MCH of 21.6 pg falls in an intermediate zone. Research suggests MCH <21.90 pg strongly indicates alpha-zero thalassemia trait 2, while this patient's MCH is just above that threshold
• The degree of anemia (Hgb 9.4 g/dL) is more severe than typically seen in thalassemia trait alone

Immediate Next Steps

Required Laboratory Studies

Following KDIGO guidelines for anemia evaluation 3, 1, obtain:

1. Serum ferritin - to assess iron stores
2. Transferrin saturation (TSAT) - to evaluate iron available for erythropoiesis
3. Absolute reticulocyte count - to assess bone marrow response
4. Serum vitamin B12 and folate levels - to exclude other nutritional deficiencies

Clinical Evaluation

Search for blood loss source, particularly:

• Gastrointestinal bleeding (most common in adults without obvious menstrual losses) 1
• Menstrual history in women
• Dietary history
• Medication review (NSAIDs, anticoagulants)

Treatment Algorithm

If Iron Deficiency Confirmed (Ferritin <100 ng/mL or TSAT <20%)

Iron supplementation is indicated when TSAT ≤30% and ferritin ≤500 ng/mL 3. Choose route based on:

• Oral iron: First-line for non-dialysis patients, trial for 1-3 months 3

  • Use if: mild deficiency, no prior intolerance, good compliance expected

• Intravenous iron: Consider if 3:

  • Severe anemia requiring rapid correction
  • Prior oral iron failure or intolerance
  • Malabsorption suspected
  • Poor compliance anticipated
  • Limited venous access not a concern

If Thalassemia Suspected

If iron studies are normal or equivocal:

• Hemoglobin electrophoresis to evaluate for thalassemia trait
• Family history assessment
• Consider genetic testing if hemoglobin electrophoresis inconclusive

Critical Pitfalls to Avoid

1. Do not assume thalassemia without iron studies - iron deficiency is far more common and treatable
2. Do not give iron supplementation without investigating blood loss - you may miss serious pathology (GI malignancy, ulcers)
3. Do not ignore the elevated RDW - this is a key discriminator favoring iron deficiency over thalassemia
4. Do not transfuse unless symptomatic - investigate and treat the underlying cause first

Clinical Context

The normal white cell and platelet counts indicate preserved bone marrow function in other cell lines, making primary bone marrow disorders unlikely 1. The elevated MPV (10.6 fL) is a minor finding of uncertain significance in this context but may reflect reactive thrombocytopoiesis.

The severity of anemia (Hgb 9.4 g/dL) warrants prompt evaluation and treatment, as anemia of this degree is associated with increased morbidity and mortality, particularly in patients with cardiovascular or renal disease 3, 1.