One of the problems with Lp(a) measurement is that the Apo(a) protein has a variable mass. It can have a molecular weight ranging from 275,000 to 800,000 daltons. This is due to variable amounts of repeating regions of the protein. Immunoassay antibodies, which recognize these regions will thus give more signal for larger Apo(a) molecules compared to smaller Apo(a) molecules. This is not ideal since again, we would prefer to quantify the number of particles but Lp(a) containing large Apo(a) molecules will produce more signal, skewing the count.
Lp(a), like CRP, is an acute phase reactant. This means that Lp(a) levels will rise in the context of general inflammation. Thus, Lp(a) should not be measured when there is extensive inflammation, such as immediately following a cardiovascular event.
Concentrations of Lp(a) above 30 mg/dL are associated with increased cardiovascular risk. The risk of having a cardiovascular event increases 2 to 3 fold if Lp(a) cholesterol is > 30 mg/dL. Fifteen to 20% of the Caucasian population have Lp(a) levels >30 mg/dL. Africans, or people of African descent, generally have levels higher than Caucasians and Asians, however, results must be evaluated in conjunction with clinical history.
Five to ten years ago, assays for Lp(a) were manual and usually deemed "research use only." However, some clinical immunoassay vendors now offer Lp(a) assays on their automated platforms.