Pathology Cheat Sheet
When Red Cells Break Early
Haemolytic anaemia for NEET-PG: intrinsic vs extrinsic, intravascular vs extravascular, haptoglobin, spherocytes, schistocytes, Heinz bodies, and Coombs test.
MedNext Academy | 3 min read
When Red Cells Break Early
Haemolytic anaemia for NEET-PG: intrinsic vs extrinsic, intravascular vs extravascular, haptoglobin, spherocytes, schistocytes, Heinz bodies, and Coombs test.
The classification and general features of haemolytic anaemia and the peripheral smear clues that identify red cell destruction.
High-yield lines
- Haemolytic anaemia is premature destruction of red cells shortening their lifespan below the normal 120 days.
- Haemolysis is classified by the site of defect as intrinsic (corpuscular) or extrinsic and by the site of destruction as intravascular or extravascular.
- Intrinsic defects are usually inherited and include membrane, enzyme, and haemoglobin disorders.
- Extravascular haemolysis occurs in the spleen and liver and produces unconjugated hyperbilirubinaemia and splenomegaly.
- Intravascular haemolysis releases free haemoglobin, causing haemoglobinuria, haemosiderinuria, and undetectable haptoglobin.
- Undetectable haptoglobin is the single most sensitive marker of intravascular haemolysis.
- All haemolysis raises reticulocytes, lactate dehydrogenase, and unconjugated bilirubin.
- Hereditary spherocytosis results from membrane skeleton defects in spectrin, ankyrin, or band 3 and shows spherocytes.
- Hereditary spherocytosis has increased osmotic fragility and improves after splenectomy.
- Schistocytes on the smear indicate microangiopathic haemolysis from fibrin strands in TTP, HUS, or DIC.
- Bite cells and Heinz bodies indicate oxidative haemolysis such as G6PD deficiency.
- The direct antiglobulin (Coombs) test detects antibody or complement coating red cells in immune haemolysis.
Mapped competency codes
- PA16.1
- PA16.2
- PA16.5
- PA16.6
Continue into the full chapter
This summary maps to PA16-hemolytic-anemia.
Frequently Asked Questions
How is haemolytic anaemia classified?
By the site of the defect as intrinsic or extrinsic to the red cell, and by the site of destruction as intravascular or extravascular.
What is the most sensitive laboratory marker of intravascular haemolysis?
An undetectable serum haptoglobin, because free haemoglobin released into plasma is completely bound and cleared.
What smear finding indicates microangiopathic haemolysis?
Schistocytes, which are fragmented red cells sheared by fibrin strands, seen in thrombotic thrombocytopenic purpura, haemolytic uraemic syndrome, and DIC.
What does a positive direct Coombs test indicate?
That red cells are coated with antibody or complement, confirming an immune-mediated haemolytic anaemia.
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