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Anaemia: Classification & Investigation
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Lesson 1 of 14
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Anaemia: Classification & Investigation
Definition
- Hb <130 g/L (males), <120 g/L (females)
Classification by MCV
| Type | MCV | Causes |
|------|-----|--------|
| Microcytic | <80 fL | Iron deficiency, thalassaemia, sideroblastic, anaemia of chronic disease (sometimes) |
| Normocytic | 80–100 fL | Acute blood loss, haemolysis, renal failure, bone marrow failure |
| Macrocytic | >100 fL | B12/folate deficiency, hypothyroidism, liver disease, alcohol, drugs (methotrexate, hydroxyurea) |
Iron Deficiency Anaemia (IDA)
- Causes: blood loss (GI, menstrual), malabsorption (coeliac), poor intake
- Blood film: microcytic hypochromic RBCs, pencil cells, target cells
- Serum ferritin Ôåô, serum iron Ôåô, TIBC Ôåæ, transferrin saturation Ôåô
- Treatment: oral ferrous sulfate 200 mg TDS; treat underlying cause
- IV iron if malabsorption, intolerance, or urgent repletion needed
B12/Folate Deficiency
- B12: pernicious anaemia (anti-intrinsic factor Ab), strict veganism, Crohn's, post-gastrectomy
- Folate: poor intake, coeliac, pregnancy (demand), methotrexate, phenytoin
- Blood film: macrocytes, hypersegmented neutrophils (>5 lobes)
- B12 deficiency: subacute combined degeneration of the cord (posterior + lateral columns)
- Treatment: IM hydroxocobalamin (B12); folic acid 5 mg OD (give B12 first to avoid masking neurology)
Haemolytic Anaemia
- Features: Ôåæ bilirubin (unconjugated), Ôåæ LDH, Ôåô haptoglobin, reticulocytosis
- Coombs (DAT) positive: autoimmune (warm/cold), drug-induced
- Intravascular: haemoglobinuria, Ôåæ plasma Hb