Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

LIPA
81558
available from multiple manufacturers and although standardization efforts are underway, currently
available methods are not standardized. Difficulties in standardizing Lp(a) mass measurement arise
from the variability in signals produced by different reagents due to the size polymorphisms of apo(a).
For this reason, some elevations of Lp(a) mass are associated with low levels of Lp(a) cholesterol. Lp(a)
quantification can be done by densitometric measurement of Lp(a) cholesterol. This method measures
only the cholesterol contained in the Lp(a) particles and is thus not influenced by the relative size of the
apo(a) size, it may provide a more specific assessment of cardiovascular risk than Lp(a) mass
measurement. Lp(a) cholesterol measurement may be used in concert with Lp(a) mass determination, or
may be used as a stand-alone test for assessment of risk.
Useful For: Evaluation of increased risk for cardiovascular disease and events: -Most appropriately
measured in individuals at intermediate risk for cardiovascular disease according to the individualsâ€
Framingham risk score -Patients with early atherosclerosis or strong family history of early
atherosclerosis without explanation by traditional risk factors should also be considered for testing
Interpretation: Patients with increased Lp(a) cholesterol values have an approximate 2-fold increased
risk for developing cardiovascular disease and events.
Reference Values:
Lp(a) CHOLESTEROL
Normal: or =3 mg/dL
LpX
Undetectable
Clinical References: 1. Berg K: Lp(a) lipoprotein: an overview. Chem Phys Lipids 1994;67-68:9-16
2. Rhoads GG, Dahlen G, Berg K et al: Lp(a) lipoproteins as a risk factor for myocardial infarction.
JAMA 1986;256:2540-2544 3. Bostom AG, Cupples LA, Jenner JL, et al: Elevated plasma lipoprotein(a)
and coronary heart disease in men aged 55 years and younger. A prospective study. JAMA
1996;276:544-548 4. Ridker PM, Hennekens CH, Stampfer MJ: A prospective study of lipoprotein(a) and
the risk of myocardial infarction. JAMA 1993;270:2195-2199 5. Tsimikas S, Brilakis ES, Miller ER, et al:
Oxidized phospholipids, Lp(a) lipoprotein, and coronary artery disease. N Engl J Med 2005;353(1):46-57
Lipoprotein (a), Serum
Clinical Information: Lipoprotein (a) (Lp[a]), first reported in 1963 by the Norwegian
physician-investigator, Kare Berg, consists of an ordinary LDL particle combined with an additional
protein. As with LDL, the Lp(a) particle contains Apolipoprotein B100 (molecular weight=approximately
512,000 D), but additionally contains Apolipoprotein a (apo[a]) (molecular weight=275,000-800,000 D),
which is covalently linked through a disulfide bond to apolipoprotein B100. Apo(a) contains a series of
amino acid repeats known as "kringles" containing 3 intrastrand disulfide bonds that are highly
homologous to similar repeats found in plasminogen. There are a total of 11 apo(a) kringle sequences; 10
of them are present as single copies, but the remaining 1(K4 type 2) varies in copy number from 3 to 40.
The copy number of the K4 type 2 kringle is genetically determined and results in a high degree of
interindividual polymorphism in the molecular mass of apo(a), which can vary from 187 kDa to 662 kDa.
The size of the Lp(a) particle varies accordingly. To date, 34 different isoforms of apo(a) have been
identified. Because of its shared homologies with LDL and plasminogen, factors thought to participate
directly or indirectly in atherogenesis, Lp(a) has been the focus of numerous clinical and epidemiologic
studies attempting to establish increased serum Lp(a) concentration as a risk factor for coronary heart
disease (CHD) and stroke. Although results of studies to date are mixed, the preponderance of evidence
strongly suggests that Lp(a) is an independent risk factor for CHD and possibly stroke, and the Lp(a)
particle has been referred to as "the most atherogenic lipoprotein." Serum concentrations of Lp(a) appear
to be largely related to genetic factors, and unfortunately, diet and lipid-lowering pharmaceuticals do not
have a major impact on Lp(a) levels. Nevertheless, measurement of serum Lp(a) may contribute to a more
comprehensive risk assessment in high-risk patients. Concentrations of Lp(a) particles in the blood can be
expressed readily either as concentrations of Lp(a)-specific protein or as Lp(a) cholesterol. Cardiovascular
Laboratory Medicine measures and reports Lp(a) cholesterol individually (LPAWS/89005 Lipoprotein [a]
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