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Test ID: LPAWS Lipoprotein (a) Cholesterol, Serum

Reporting Name

Lp(a) Cholesterol, S

Useful For

Evaluation of increased risk for cardiovascular disease and events:

-Most appropriately measured in individuals at intermediate risk for cardiovascular disease

-Patients with early atherosclerosis or strong family history of early atherosclerosis without explanation by traditional risk factors should also be considered for testing

 

Follow-up evaluation of patients with measurable lipoprotein(a) protein (LIPA)

Specimen Type

Serum


Specimen Required


Patient Preparation: Fasting (8 hours before collection and abstain from alcohol for 24 hours before collection)

Collection Container/Tube: 

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 0.4 mL


Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  60 days

Reference Values

Lp(a) CHOLESTEROL

Normal: <3 mg/dL

Suggests increased risk of coronary artery disease: ≥3 mg/dL

 

LpX

Undetectable

Day(s) and Time(s) Performed

Monday through Friday; 10 a.m.

Test Classification

This test has been modified from the manufacturer’s instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

83700

LOINC Code Information

Test ID Test Order Name Order LOINC Value
LPAWS Lp(a) Cholesterol, S In Process

 

Result ID Test Result Name Result LOINC Value
2849 Lp(a) Cholesterol 10835-7
23924 LpX 42178-4
23937 Interpretation 59462-2

Clinical Information

Lipoprotein(a) (Lp[a]) is a highly heterogeneous molecule, consisting of a low-density lipoprotein (LDL) with a highly glycosylated apolipoprotein(a) (apo[a]) covalently linked to the apolipoprotein B moiety of LDL via a single disulfate bond. Lp(a) has been associated with atherogenesis and promotion of thrombosis. Increased levels of Lp(a) have been estimated to confer a 1.5 to 3.0-fold increased risk for coronary artery disease (CAD) in many but not all studies. Apo(a) has approximately 80% structural homology with plasminogen, but does not contain the active site for fibrin cleavage. One proposed mechanism for Lp(a)'s atherogenicity is competition for binding sites with plasminogen during fibrin clot formation and the resulting inhibition of fibrinolysis. Recently a high correlation was demonstrated between Lp(a) and oxidized LDL, suggesting that the atherogenicity of Lp(a) lipoprotein may be mediated in part by associated proinflammatory oxidized phospholipids.

 

The heterogeneity of Lp(a) arises mainly from the variable number of kringle repeats in the apo(a) portion of the molecule. Kringles are specific structural domains containing 3 intra-strand disulfide bonds that are highly homologous to similar repeats found in plasminogen.

 

In the clinical laboratory, immunologic methods are generally used to quantify Lp(a) protein mass. Reagents for Lp(a) mass measurement are 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) particle. Because Lp(a) cholesterol measurement is not influenced by 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.

Interpretation

Patients with increased Lp(a) cholesterol values have an approximate 2-fold increased risk for developing cardiovascular disease and events.

 

Lipoprotein-X (LpX) is an abnormal lipoprotein that appears in the sera of patients with obstructive jaundice, and is an indicator of cholestasis. The presence of LpX will be reported if noted during Lp(a) cholesterol analysis.

Clinical Reference

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

6. Baudhuin LM, Hartman SJ, O'Brien JF, et al:  Electrophoretic measurement of lipoprotein(a) cholesterol in plasma with and without ultracentrifugation: comparison with an immunoturbidimetric lipoprotein[a] method. Clin Biochem 2004 June;37[6]:481-488

7. McConnell JP, Baudhuin LM, Berger PB, et al: Lipoprotein (a) cholesterol, but not Lp(a) mass, is an independent predictor of angiographic coronary artery disease and subsequent cardiovascular events in patients referred for coronary angiography. Circulation 2007;116:II_818

Analytic Time

2 days (not reported on Saturday or Sunday)

Method Name

Electrophoresis, Enzyme Staining, and Densitometry

Forms

If not ordering electronically, complete, print, and send a Cardiovascular Test Request Form (T724) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/cardiovascular-request-form.pdf).

Mayo Medical Laboratories | Cardiology Catalog Additional Information:

mml-lipids-lipoproteins