Microcytic Anemia with Elevated RDW - Likely Iron Deficiency or Thalassemia
These laboratory values indicate microcytic, hypochromic anemia with increased red cell size variation, most commonly caused by iron deficiency, though thalassemia trait must be excluded given the elevated RBC count.
Interpretation of Your Values
Your results show a classic pattern of microcytic anemia:
- MCV 71.8 fL (microcytic, <80 fL) - red cells are smaller than normal 1
- MCH 21.2 pg (hypochromic, low) - each red cell contains less hemoglobin 1
- MCHC 29.6 g/dL (low) - reduced hemoglobin concentration within cells 1
- RDW 16.8% (elevated) - significant variation in red cell sizes, indicating mixed populations of cells 2
- RBC 5.93 million/µL (elevated) - your body is compensating by producing more red cells
Most Likely Diagnoses
Primary Consideration: Iron Deficiency Anemia
Iron deficiency is the most common cause of microcytic anemia 1. The elevated RDW is particularly suggestive, as it increases early in iron deficiency when a microcytic population begins appearing alongside normal cells 3. The combination of low MCV, MCH, and MCHC with elevated RDW has 82.3% sensitivity for iron deficiency 3.
Critical Alternative: Thalassemia Trait
The elevated RBC count (5.93) raises concern for thalassemia trait, particularly beta-thalassemia, where the MCV is typically reduced out of proportion to anemia and the RBC count is often elevated 2. In thalassemia, MCV ≤73.8 fL and MCH ≤21.9 pg have >90% sensitivity for beta-thalassemia trait versus E-trait 4. Your values fall into this range.
Required Next Steps
Immediate Testing Required
Serum ferritin - the single most powerful test for iron deficiency 2, 5:
- <15 μg/L confirms iron deficiency
- <30 μg/L indicates low iron stores
100 μg/L essentially excludes iron deficiency 2
Complete iron studies if ferritin is equivocal 1:
- Transferrin saturation <15% suggests iron deficiency
- Total iron binding capacity (TIBC)
Hemoglobin electrophoresis if iron studies are normal 2, 5 - essential to exclude thalassemia, especially if you have Mediterranean, Middle Eastern, African, or Southeast Asian ancestry
Diagnostic Algorithm
If ferritin <30 μg/L: Proceed with iron deficiency workup
If ferritin normal with appropriate ethnic background: Obtain hemoglobin electrophoresis to diagnose thalassemia 2, 5
If both normal: Consider anemia of chronic disease, though less likely with this degree of microcytosis 1
Investigation for Underlying Cause (If Iron Deficiency Confirmed)
All adults with confirmed iron deficiency anemia require gastrointestinal evaluation to exclude malignancy 2. The British Society of Gastroenterology guidelines mandate 2:
- Upper endoscopy with small bowel biopsies (2-3% have celiac disease) 2
- Colonoscopy or barium enema - dual pathology occurs in ~10% of cases 2
- Both examinations are required even if one reveals pathology, unless cancer or celiac disease is found 2
Exception to GI Investigation
Pre-menopausal women with heavy menstrual bleeding may not require immediate GI workup if they respond appropriately to iron therapy 2. However, investigation should still be considered if anemia persists despite treatment.
Common Pitfalls to Avoid
- Do not assume dietary deficiency explains the anemia - full GI investigation is still required even with poor diet 2
- Do not miss thalassemia - the elevated RBC count is a red flag that distinguishes it from pure iron deficiency 2
- Do not rely on ferritin alone if inflammation is present - chronic disease, malignancy, or liver disease can falsely elevate ferritin above 12-15 μg/L despite true iron deficiency 2
- Do not stop investigation at mild anemia - even mild anemia can indicate serious pathology including GI malignancy 2
Clinical Significance
The elevated RDW (16.8%) is particularly important as it indicates active changes in red cell production and has been associated with increased cancer risk in large cohort studies 6. This underscores the importance of thorough investigation rather than empiric iron supplementation alone.