Interpret the complete blood count results showing hemoglobin 7.8 g/dL, hematocrit 27.7 %, mean corpuscular volume 71 fL, mean corpuscular hemoglobin 20 pg, mean corpuscular hemoglobin concentration 28.2 g/dL, and red cell distribution width 18.7 %.

Microcytic Hypochromic Anemia with Severe Iron Deficiency

This CBC demonstrates severe microcytic hypochromic anemia with marked anisocytosis, most consistent with iron deficiency anemia, requiring immediate iron studies (ferritin, serum iron, TIBC, transferrin saturation) to confirm the diagnosis and guide treatment.

Key Findings

The CBC reveals several critical abnormalities:

• Severe anemia: Hemoglobin 7.8 g/dL (normal 11.1-15.9) - this is significantly below normal and requires urgent evaluation
• Microcytosis: MCV 71 fL (normal 79-97) - red cells are markedly smaller than normal
• Hypochromia: MCH 20.0 pg (normal 26.6-33.0) and MCHC 28.2 g/dL (normal 31.5-35.7) - red cells contain insufficient hemoglobin
• High RDW: 18.7% (normal 11.7-15.4) - indicates significant variation in red cell size (anisocytosis)

Diagnostic Interpretation

The combination of low MCV, low MCH, low MCHC, and elevated RDW creates a classic pattern for iron deficiency anemia 1. The guideline framework classifies microcytic anemias as primarily caused by nutritional iron deficiency, iron loss from gastrointestinal disease, iron malabsorption, hemoglobinopathies, or anemia of chronic disease 1.

The elevated RDW is particularly important - it distinguishes iron deficiency from thalassemia trait, where RDW is typically normal 2, 3. In iron deficiency, RDW increases as the body produces increasingly smaller and more variable red cells over time 4.

Required Next Steps

Immediate Laboratory Workup:

• Serum ferritin (expect <15 µg/L in iron deficiency)
• Serum iron and TIBC (expect low iron, high TIBC)
• Transferrin saturation (expect <15%)

Critical Caveat:

If ferritin is elevated (>20 mg/L) or transferrin saturation is elevated despite the microcytic picture, consider genetic disorders of iron metabolism or hemoglobinopathies 1. In this scenario, hemoglobin electrophoresis or HPLC would be indicated 3.

Differential Diagnosis Priority

1. Iron deficiency anemia (most likely given the pattern)

   • Nutritional deficiency
   • Chronic blood loss (GI bleeding, menorrhagia)
   • Malabsorption

2. Thalassemia trait (less likely due to high RDW)

   • Would show MCV ≤73.8 fL and MCH ≤21.9 pg with normal or low-normal RDW 3

3. Anemia of chronic disease (possible but less typical)

   • Usually normocytic or mildly microcytic
   • Ferritin would be normal or elevated

Clinical Pitfalls to Avoid

• Do not assume iron deficiency without confirming iron studies - ferritin and transferrin saturation are essential 1
• Do not overlook hemoglobinopathies in appropriate ethnic populations - Southeast Asian, Mediterranean, or African ancestry increases thalassemia risk 3
• Do not miss occult GI bleeding - in adults, especially males and postmenopausal females, investigate for GI sources
• Do not ignore the severity - hemoglobin of 7.8 g/dL may require transfusion depending on symptoms and comorbidities

Pattern Recognition

The specific values (MCV 71, MCH 20.0, MCHC 28.2, RDW 18.7) fall well outside normal ranges and demonstrate the characteristic progression of iron deficiency 2. As iron stores deplete, the body first produces smaller cells (low MCV), then cells with less hemoglobin (low MCH and MCHC), with increasing size variation (high RDW) as the deficiency worsens 4.