General Medicine
Anaemia
Anaemia for MBBS: morphological classification, iron studies, macrocytic and haemolytic anaemia, replacement therapy and transfusion, mapped to NMC codes IM9.1 to IM9.21.
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Anaemia
Anaemia for MBBS: morphological classification, iron studies, macrocytic and haemolytic anaemia, replacement therapy and transfusion, mapped to NMC codes IM9.1 to IM9.21.
This chapter builds a morphological approach to anaemia using the red cell indices and peripheral smear, then works through the common causes in the Indian context. It emphasises iron studies, the workup of macrocytic and haemolytic anaemia, rational replacement therapy and transfusion indications.
High-yield: Anaemia
- Anaemia is classified by red cell size into microcytic, normocytic and macrocytic patterns using the mean corpuscular volume.
- Iron deficiency is the commonest cause of microcytic anaemia and of anaemia overall in India.
- In iron deficiency the ferritin is low, the total iron-binding capacity is high and the transferrin saturation is low.
- Ferritin is an acute phase reactant, so a normal value does not exclude iron deficiency in inflammation.
- The peripheral smear gives valuable clues such as microcytic hypochromic cells, target cells or hypersegmented neutrophils.
- Macrocytic anaemia with hypersegmented neutrophils suggests vitamin B12 or folate deficiency.
- Vitamin B12 deficiency can cause subacute combined degeneration of the cord and must be corrected before folate to avoid worsening it.
- A raised reticulocyte count points to haemolysis or blood loss rather than a production defect.
- Thalassaemia and iron deficiency both cause microcytosis, but the Mentzer index and iron studies help separate them.
- The anaemia of chronic disease is typically normocytic with low serum iron but normal or raised ferritin.
- Bone marrow examination is reserved for unexplained anaemia, pancytopenia or suspected marrow infiltration.
- Replacement therapy uses oral iron for deficiency, with intravenous iron or transfusion reserved for specific indications.
- Iron is best absorbed on an empty stomach and vitamin C enhances its absorption.
- National programmes address nutritional anaemia in pregnant women, children and adolescents.
- Transfusion is guided by symptoms and haemodynamic status rather than the haemoglobin figure alone.
Anaemia by red cell size
- **Microcytic:** Iron deficiency (low ferritin, high iron-binding capacity), thalassaemia and anaemia of chronic disease.
- **Macrocytic:** Vitamin B12 or folate deficiency with hypersegmented neutrophils on the smear.
- **Normocytic:** Acute blood loss, haemolysis (high reticulocytes) or anaemia of chronic disease.
- **Treatment:** Oral iron for deficiency; correct B12 before folate; transfuse by symptoms not by number.
NMC competencies in this chapter
- **IM9.1:** Definition and classification of anaemia
- **IM9.2:** Morphology, aetiology and prevalence of anaemia
- **IM9.7:** Components of the haemogram and their utility
- **IM9.8:** Tests for iron deficiency
- **IM9.10:** Peripheral smear and stool occult blood
- **IM9.13:** Replacement therapy with iron, vitamin B12 and folate
- **IM9.17:** Indications for blood transfusion and components
- **IM9.20:** Counselling to prevent nutritional anaemia
Frequently Asked Questions
How is anaemia classified?
Anaemia is classified by the mean corpuscular volume into microcytic, normocytic and macrocytic patterns, which directs the differential and the choice of confirmatory tests.
What are the iron study findings in iron deficiency?
Iron deficiency shows a low ferritin, low serum iron, high total iron-binding capacity and low transferrin saturation, though ferritin can be falsely normal in inflammation.
Why correct vitamin B12 before folate?
Giving folate alone to a B12-deficient patient can improve the anaemia but allow subacute combined degeneration of the cord to progress, so B12 is corrected first.
How does this chapter help for NEET-PG?
The morphological classification, iron study patterns, smear findings and the B12 before folate rule are frequently tested and map directly to exam questions.
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