Haptoglobin 2-2 (Hp 2-2) is the least effective of the three haptoglobin phenotypes in binding free hemoglobin and therefore provides less antioxidant benefits than Hp 1-1. Hp 2-2 is associated with renal failure, familial epilepsy, hypertension, atherosclerosis and coronary heart diseases. Individuals who are phenotype 2-2 have the lowest concentration of haptoglobin in plasma.