Lp (a) is a modified version of LDL containing a unique protein, apolipoprotein (a). This lipoprotein was discovered in 1963 and is now well-associated with vascular disease. It is important not to confuse apolipoprotein (a) with apolipoprotein A that is found on high density lipoprotein particles. Lipoprotein (a) is abbreviated as Lp(a). Lp(a) is an LDL particle whose ApoB molecule has formed a disulfide bond with another protein called Apo(a). See figure. Apo(a) is a protein very similar in structure to plasminogen.
Numerous retrospective case control studies and prospective studies have shown Lp(a) to be an independent risk factor for vascular disease. This means that Lp(a) levels alone (not in conjunction with LDL or other patient risk factors) can help predict cardiovascular risk.
Lp(a) has been called the most atherogenic lipoprotein. Serum concentrations of Lp(a) are related to genetic factors; drugs and diet changes do not typically lower Lp(a) as they do LDL.