The haptoglobin is an α-glycoprotein, synthesized in the liver, and it is able to bind irreversibly to haemoglobin. The haptoglobin complexes and also the free haptoglobin play an important role in the iron conservation and in the prevention of possible renal damages produced by haemoglobin excretion. Haptoglobin concentration, as an acute phase protein increases as a result of inflammation, tissue necrosis or neoplasia. Levels of haptoglobin are decreased in plasma as a consequence of in vivo haemolysis, presence of oestrogens in the pregnancy, the contraceptive therapy as well as many acute or chronic liver diseases including the acute viral hepatitis.

The haptoglobin assay is mainly used detect and evaluate haemolytic anaemia as well as to distinguish it from other causes of anaemia. It is considered to be a very sensitive indicator of intravascular haemolysis because under normal circumstances 1% of RBC are destroyed. An increase of more than 2% of destruction will reduce completely the haptoglobin concentration in absence of production stimulus as inflammations or corticoid therapy.