=====Haptoglobin=====
Haptoglobin (abbreviated as Hp) is the protein that in humans is encoded by the HP gene.

In blood [[plasma]], haptoglobin binds free [[hemoglobin]] (Hb) released from [[erythrocyte]]s with high affinity and thereby inhibits its oxidative activity. The haptoglobin-hemoglobin complex will then be removed by the [[reticuloendothelial system]] (mostly the spleen). In clinical settings, the haptoglobulin assay is used to screen for and monitor intravascular hemolytic [[anemia]]. In intravascular hemolysis, free hemoglobin will be released into circulation and hence haptoglobin will bind the hemoglobin. This causes a decline in haptoglobin levels. Conversely, in extravascular hemolysis the reticuloendothelial system, especially splenic [[monocyte]]s, phagocytose the erythrocytes and hemoglobin is relatively not released into circulation; however, excess hemolysis can release some hemoglobin causing haptoglobin levels to be decreased. Therefore haptoglobin is not a reliable way to differentiate between intravascular and extravascular hemolysis.

Haptoglobin (Hp) [[genotype]] has been shown to be a predictor of clinical outcomes in [[subarachnoid hemorrhage]]. 

In humans, two alleles for haptoglobin have been described that give rise to different haptoglobin proteins and three major genotypes, haptoglobin 1/1, 2/1, and 2/2 
((Asleh R, Levy AP: In vivo and in vitro studies establishing haptoglobin as a major susceptibility gene for diabetic vascular disease. Vasc Health Risk Manag1 :19 –28,2005)).

see [[Haptoglobin 2 2 genotype]]