haptoglobin (Hp)

Introduction

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