Lipoprotein (a), Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Providing additional information on coronary heart disease (CHD) risk in patients known or suspected to be at increased risk based on other factors, including family history of premature CHD or stroke, hypertension, cigarette smoking, obesity, diabetes mellitus, increased concentration of LDL cholesterol, and depressed concentration of HDL cholesterol.
Automated Turbidimetric Immunoassay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Lipoprotein (a), S
Lipoprotein (a), S
Lipoprotein a, S MMLNE
Lipoprotein a, S MMLNE
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: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions: Fasting-overnight (12-14 hours)
Additional Information: Because Lp(a) acts like an acute-phase protein, it should not be measured during periods of active inflammation. Lp(a) levels should not be measured for at least 1 month following a myocardial infarction or stroke.
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 reject
Mild OK; Gross reject
Mild OK; Gross reject
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]), 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] Cholesterol, Serum) and as a part of the lipoprotein profile (LMPP/83673 Lipoprotein Metabolism Profile). The cholesterol content of Lp(a) particles varies little, and Lp(a) cholesterol can be quantified readily. In many cases, we have observed Lp(a) cholesterol to be at levels of 25 mg/dL to 50 mg/dL, and in some cases to be >100 mg/dL. Thus, Lp(a) can contain significant proportions of the serum cholesterol. In such cases, knowledge of the concentration of Lp(a) and of the contribution of Lp(a) cholesterol to the serum total cholesterol should be helpful to physicians in their evaluation of cardiovascular risk levels.
Unlike Lp(a) cholesterol, accurate immunochemical measurement of Lp(a)-specific protein, is complicated by a number of factors. A significant problem is the issue of how to express the result of a quantitative test for Lp(a)-specific protein in meaningful terms. Because the molecular size of Lp(a)-specific protein varies over a broad range in the population (240,000-800,000 D), a test result primarily related to the number of molecules of Lp(a)-specific protein in a specimen cannot be expressed accurately or meaningfully in terms of mg protein/dL unless the molecular weight of the Lp(a)-specific protein in that specimen has been determined. An additional related concern is that the degree of atherogenicity of the Lp(a) particle in any specific case may depend on the molecular size of the Lp(a)-specific protein.
Alteration in serum Lp(a) concentration secondary to diet modification, exercise, or drug therapy is minimal. Therefore, it is inappropriate to use Lp(a) as a general screening test in the healthy population. However, in a patient with additional modifiable CHD risk factors, more aggressive therapy to normalize these factors may be indicated if the Lp(a) value is also increased.
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.
< or =30 mg/dL
Values >30 mg/dL may suggest increased risk of coronary heart disease.
The frequency distribution of serum lipoprotein (a) (Lp[a]) concentrations is markedly skewed toward the low end, with approximately 85% of the population having concentrations <30 mg/dL.
Concentrations >30 mg/dL have been associated with increased risk of coronary heart disease in numerous studies. Observations over the last 3 decades have indicated that Lp(a) increases cardiovascular risk 2 to 3-fold when its level in the blood plasma is >30 mg/dL (correspondingly, Lp[a] cholesterol would be >5 mg/dL). Lp(a) concentrations of < =15 mg per dL (Lp[a] cholesterol < or =5 mg per dL) appear not to confer an increased risk. Multivariate analysis suggests that Lp(a) functions independently of the more conventional risk factors (eg, increased LDL cholesterol, cigarette smoking, diabetes). Although some recent observations have indicated that Lp(a)-associated cardiovascular risk is significant only when the concentration of the companion risk factor, LDL, also is increased.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The epidemiologic database is most extensive for the Caucasian population. Studies on Asians (specifically Chinese, Japanese, and Koreans) indicate that lipoprotein (a) (Lp[a]) is a comparable risk factor for atherosclerosis in these groups as well. In African Americans, the median Lp(a) serum concentration is 2 to 3 times higher than in Caucasians. However, insufficient epidemiologic data are available on the African American population to equate the role of Lp(a) as a risk factor in African Americans.
Because Lp(a) behaves like an acute-phase protein, it should not be measured during periods of active inflammation. Serum Lp(a) levels should not be measured for a least 1 month after a myocardial infarction or stroke.
In most cases, the preferred test for quantifying Lp(a) is LPAWS/89005 Lipoprotein (a) Cholesterol, Serum.
Not recommended as a screening test in the healthy population.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Utermann G: The mysteries of lipoprotein(a). Science 1989;246:904-910
2. Lackner C, Cohen JC, Hobbs HH: Molecular definition of the extreme size polymorphism in apolipoprotein(a). Hum Mol Genet 1993;2:933-940
3. Schaefer EJ, Lamon-Fava S, Jenner JL, et al: Lipoprotein(a) levels and risk of coronary heart disease in men. The Lipid Research Clinics Coronary Primary Prevention Trial. JAMA 1994;271:999-1003
4. Ridker PM, Hennekens CH, Stampfer MJ: A prospective study of lipoprotein(a) and the risk of myocardial infarction. JAMA 1993;270:2195-2199
Method Description Describes how the test is performed and provides a method-specific reference
This test uses an automated turbidimetric immunoassay method to measure Lp(a) in serum or EDTA plasma. Serum (or plasma) is first incubated with a polymeric enhancer. Following initial incubation and measurement of specimen blank, undiluted antiserum specific to human Lp(a) is added. The specimen solution is mixed and insoluble antigen-antibody complexes begin to form. The complexes that form produce turbidity in the mixture and increase the amount of light scatter. The decrease in percent transmittance of light is measured and is proportional to the amount of Lp(a) in the specimen. (Levine DM, Sloan DJ, Donner JE, et al: Automated measurement of lipoprotein[a] by immunoturbidimetric analysis. Int J Clin Lab Res 1992;22:173-178)
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 Saturday; Continuously
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.
1 day (not reported on 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 cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified 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|
|LIPA||Lipoprotein (a), S||10835-7|