Lipoprotein (a) Cholesterol, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
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
Electrophoresis, Enzyme Staining, and Densitometry
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Lp(a) Cholesterol, S
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 0.4 mL
Collection Instructions: Fasting (8 hours)
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross OK
Mild OK; Gross OK
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||7 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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)â€™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.
Lack of standardization of assays and apo(a) heterogeneity may partially account for these discrepancies. 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) 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.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
Normal: <3 mg/dL
Suggests increased risk of coronary artery disease: > or =3 mg/dL
Patients with increased Lp(a) cholesterol values have an approximate 2-fold increased risk for developing cardiovascular disease and events.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Lp(a) cholesterol values should not be confused with Lp(a) mass values, although they are highly correlated. Lp(a) cholesterol values will be approximately 10X lower than Lp(a) mass values, but the difference between the measures is not uniform. Lp(a) mass values are considered elevated when >30 mg/dL. Lp(a) cholesterol is increased if > or =3 mg/dL.
Lp(a) cholesterol and Lp(a) mass were compared in 504 patients who underwent clinically indicated angiography. Although both were correlated to the angiographic coronary disease, Lp(a) cholesterol was the more strongly related disease. Lp(a) cholesterol, but not Lp(a) mass, was associated with cardiovascular outcomes in that study (manuscript in preparation).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
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
Method Description Describes how the test is performed and provides a method-specific reference
Serum sample is applied to agarose gel (Helena Laboratories, Beaumont, TX). Electrophoresis is carried out for 40 minutes at 250 volts, facilitating separation of the lipoprotein bands. Following electrophoresis, the lipoprotein bands are stained with enzymatic reagent (Helena) containing cholesterol esterase, cholesterol dehydrogenase, and diaphorase. The percent area of the densitometric trace corresponding to Lp(a) is multiplied by the total cholesterol value to obtain Lp(a) cholesterol value (mg/dL). (Baudhuin LM, Hartman SJ, Oâ€™Brien JF, et al: Electrophoretic measurement of lipoprotein(a) cholesterol in plasma with and without ultracentrifugation: comparison with an immunoturbidimetric liproprotein[a] method. Clin Biochem 2004 June;37:481-488)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; 10 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
2 days (not reported on Saturday or Sunday)
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|