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PA14.1-2 | Peripheral Smear in Microcytic Anaemia: Hands-on Interpretation — Part 3

The Side-by-Side Challenge Panel — Read the Four Smears

You have now seen each smear pattern individually. Now test your integration: four smears from four different patients with microcytic anaemia. Each smear is real. Each has a diagnosis hidden behind it.

For each panel:
1. Describe what you see (size, colour, shape, inclusions)
2. Note the key distinguishing feature
3. Generate your diagnosis
4. State your next investigation

Then reveal the answer.

This panel is designed as an H5P Image Hotspots interaction. Each smear has hotspot markers on the key diagnostic feature — click to reveal the finding name and the diagnosis.

Panel A: Microcytic hypochromic RBCs, pencil cells present, anisocytosis, few target cells. RDW = 19.2%.
Panel B: Microcytic RBCs with PROMINENT target cells (multiple per field), mild hypochromia, RBC count 5.9 million, RDW = 12.4%.
Panel C: Two distinct RBC populations — small pale cells and normal pink cells — in the same field. Pappenheimer bodies noted. RDW = 23.1%.
Panel D: Microcytic RBCs with coarse blue stippling in many cells. Occupation: battery factory worker.

Four-panel comparison showing different blood smear patterns for microcytic anemia diagnosis including iron deficiency, thalassemia, sideroblastic anemia, and lead poisoning. — **Panel A:** Iron deficiency anemia showing pencil cells, anisocytosis, hypochromic RBCs, elevated RDW. **Panel B:** Thalassemia showing prominent target cells, mild microcytosis, uniform morphology, normal RDW. **Panel C:** Sideroblastic anemia showing dimorphic RBC populations, Pappenheimer bodies, markedly elevated RDW. **Panel D:** Lead poisoning showing coarse basophilic stippling in microcytic RBCs, occupational exposure history.

SELF-CHECK

A 22-year-old Sindhi female medical student is found to have Hb 11.2 g/dL, MCV 64 fL, RBC count 5.6 million/µL, RDW 12.6%, serum ferritin 42 ng/mL (normal). Her smear shows prominent target cells, mild microcytosis, and mild hypochromia. RBC size is uniform. What does this smear pattern indicate, and what is the single most important next investigation?

A. Iron deficiency anaemia — start oral iron supplementation immediately

B. Anaemia of chronic disease — screen for occult inflammatory disease

C. Beta-thalassaemia trait — order HPLC for HbA2 quantification (diagnostic cutoff: HbA2 >3.5%)

D. Hereditary spherocytosis — order osmotic fragility test

Reveal Answer

Answer: C. Beta-thalassaemia trait — order HPLC for HbA2 quantification (diagnostic cutoff: HbA2 >3.5%)

This is a classic thalassaemia trait presentation: disproportionate microcytosis (MCV 64) with MILD anaemia (Hb 11.2), ELEVATED RBC count (5.6 million — the marrow compensates with more but smaller cells), NORMAL ferritin (ruling out IDA), LOW RDW (12.6% — uniform microcytosis), and PROMINENT target cells on the smear. The Sindhi ethnic background raises prior probability (beta-thalassaemia trait prevalence ~3–5% in Sindhi and Gujarati populations). HPLC will show elevated HbA2 (>3.5%) and possibly mildly elevated HbF. The critical counselling implication: partner testing and genetic counselling before pregnancy. Iron therapy is NOT indicated — ferritin is normal and giving iron to a thalassaemia carrier without iron deficiency causes iron overload.