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Diagnostic Approach to Anaemia

Anaemia is defined as < 120g/L in women and < 130g/L in men. It's classified in 3 ways:

  • Microcytic - MCV < 80FI

  • Normocytic - MCV 80-100FI

  • Macrocytic - MCV > 100FI


Clinical features:

  • Symptoms - Fatigue, SOB, Dizziness, Headache, Palpitations

  • Signs - Pale skin, Conjunctival pallor, Tachycardia, Tachypnoea

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Microcytic anaemia

  • Iron-deficiency - Most common

  • Thalassaemia

  • Anaemia of chronic disease

  • Lead poisoning

  • Sideroblastic anaemia (very rare)


N.B. Sideroblastic anaemia presents very similarly to IDA, but is refractory to intensive iron therapy, and has an atypically high serum ferritin and iron.


Normocytic anaemia

3 A’s and 2 H’s:

  • Acute blood loss

  • Aplastic anaemia (Bone Marrow Failure) - Suspect if pancytopenic

  • Anaemia of chronic disease

  • Haemolytic anaemia

  • Hypothyroidism


Macrocytic anaemia

  • Megaloblastic - B12 or Folate deficiency, Drugs

  • Non-megaloblastic - Alcohol, Hypothyroidism, Liver disease, Reticulocytosis


The most common cause of B12 deficiency is Percinious anaemia, which is an autoimmune attack of gastric parietal cells by autoantibodies against Intrinsic Factor, which is needed for B12 absorption in the terminal ileum. It's managed with Cobalamin (life-long replacement).



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