haptoglobin (Hp)

see also:

• haemolytic anaemia
• lactic dehydrogenase (LDH)

• serum haptoglobin is used as a marker of haemolytic anaemia and is also an acute phase reactant
• haptoglobin binds free haemoglobin and the complexes are then removed from circulation by the reticuloendothelial system, mostly, by the spleen.
• intravascular or significant extravascular haemolysis thus REDUCES serum haptoglobin levels
• some people have genetically low levels of haptoglobin and this is associated with:
  • diabetic nephropathy
  • IHD in type 1 diabetes
  • Crohn's disease
  • altered inflammatory disease behaviour
  • primary sclerosing cholangitis
  • susceptibility to idiopathic Parkinson's disease
  • reduced incidence of Plasmodium falciparum malaria
• some studies associate certain haptoglobin phenotypes with the risk of developing schizophrenia.

• haptoglobin is an acute phase reactant and levels may rise with acute stresses:
  • infection, extreme stress, burns, major crush injury, allergy, etc

• this may support a diagnosis of haemolytic anaemia, especially if there is also:
  • anaemia and reduced RBC and haematocrit
  • increased reticulocyte count

• may indicate RBC destruction within the reticuloendothelial system such as occurs with:
  • drug-induced haemolytic anaemia
  • RBC dysplasias

• suggests decreased RBC production
  • aplastic anaemia, etc