Haemolytic anaemia

Anaemia due to shortened survival of circulating RBCs due to their premature destruction

Pathophysiology

• Laboratory features are related to:
  • Haemolysis
    • Extravascular
      • Unconjugated bilirubin increased
      • AST increased
    • Intravascular
      • Haemoglobinuria
      • LDH increased
      • Haptoglobin reduced
  • Erythropoietic response of the bone marrow
• Compensated haemolysis vs haemolytic anaemia

Presentation

• Acute haemolysis
  • Rapid fall in Hb concentration with increased reticulocyte count (at least 4-5%) in the absence of blood loss
  • The elevated reticulocyte count can't be explained by accelerated RBC production due to recent bleeding, repletion of iron, vitamin B12, folate or copper, or administration of EPO
  • Combination of increased LDH and reduced haptoglobin is 90% specific
  • Normal LDH and haptoglobin is >25mg/dL is 92% sensitive
• Chronic haemolysis
  • Stable Hb, high reticulocyte count, normal LDH, normal bilirubin

Finding	Change in hemolytic anemia
Anemia*	Decreased hemoglobin Decreased hematocrit
Bone marrow response/recovery	Increased reticulocyte count Underestimation of HbA1C
Release of RBC contents	Increased LDH Increased indirect bilirubin Decreased haptoglobin Hemoglobinemia in intravascular hemolysis¶ Hemoglobinuria in intravascular hemolysis¶
RBC morphology changesΔ	Spherocytes or microspherocytes in immune hemolysis Schistocytes in microangiopathic hemolysis Blister or bite cells in oxidant injury Sickle cells in sickle cell disease Target cells and teardrop cells in thalassemia