Expansion
Microcytic, normocytic and macrocytic, each with a short differential
Expansion
Microcytic (MCV under 80) - TAILS
- T - Thalassaemia
- A - Anaemia of chronic disease (usually normocytic, sometimes microcytic)
- I - Iron deficiency, by far the commonest
- L - Lead poisoning
- S - Sideroblastic anaemia
Normocytic (80 to 100)
- Acute blood loss, anaemia of chronic disease, chronic kidney disease, haemolysis, marrow failure, mixed deficiency, pregnancy
Macrocytic (over 100)
- Megaloblastic: B12 and folate deficiency, methotrexate, hydroxycarbamide. Hypersegmented neutrophils on film
- Non-megaloblastic: alcohol, liver disease, hypothyroidism, myelodysplasia, reticulocytosis, pregnancy
Iron studies separate the two commonest microcytic causes: iron deficiency gives low ferritin, low iron, high transferrin and low saturation, while anaemia of chronic disease gives normal or high ferritin with low transferrin, reflecting hepcidin-driven sequestration.
Thalassaemia trait is suggested by a disproportionately low MCV for the degree of anaemia with a normal or high red cell count.