At a Glance
Why Get Tested?
When to Get Tested?
When you have a family history of elevated Lp(a) and/or a family history of premature CVD; when you have heart disease but your lipid profile is normal or shows only mildly elevated cholesterol and/or low-density lipoprotein cholesterol (LDL-C)
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None; however, if performed at the same time as a lipid profile, fasting for 9-12 hours may be required. In this case, only water is permitted.
The Test Sample
What is being tested?
Lp(a) is a lipoprotein that is similar to low-density lipoprotein (LDL) in that it contains a single ApoB protein along with cholesterol and other lipids. Like LDL, its presence is considered a risk factor for cardiovascular disease (CVD). It differs from LDL mainly by the presence of a second protein component, called apolipoprotein(a), that is attached to the ApoB protein. Apolipoprotein(a) has an unusual structure: a series of repeat subunits (often called kringles) that resemble the clot-dissolving protein plasmin. It is thought that the apolipoprotein(a) portion of Lp(a) inhibits the action of plasmin, preventing clots from being broken down normally. It is thought that Lp(a) also promotes the uptake of LDL into blood vessel walss. Thus Lp(a) has two potential ways to contribute to development of atherosclerotic plaque formation: deposition of LDL and accumulation of clots in the arteries. For this reason, Lp(a) could potentially increase the risk of atherosclerosis more than LDL.
The apolipoprotein(a) portion varies in size in different individuals due to different numbers of repeating subunits. The number of subunits is genetically determined. Caucasians tend to have small apolipoprotein(a) sizes while those of African ancestry tend to have larger apolipoprotein sizes. The significance of the variation in size in contributing to CVD risk is complex. There is some evidence that small size forms of Lp(a) increase the risk of atherosclerosis more than the larger forms. This finding may explain why Lp(a) in Caucasians seems to be a more significant risk factor than Lp(a) in those of African ancestry. Most Lp(a) tests do not measure the size of apolipoprotein(a). They measure and report only the level in blood.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed; however, since this test may be performed at the same time as a lipid profile, fasting for 9-12 hours may be required.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Zieve, D. and Dugdale, D. (Updated 2010 May 23). Lipoprotein-a. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/007262.htm. Accessed September 2010.
Delgado, J. et. al. (Updated 2010 April). Cardiovascular Disease (Non-traditional Risk Markers) - Risk Markers - CVD (Non-traditional). ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/CVDRiskMarkerNontrad.html?client_ID=LTD through http://www.arupconsult.com. Accessed September 2010.
(© 1995–2010). Unit Code 81558: Lipoprotein (a), Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81558 through http://www.mayomedicallaboratories.com. Accessed September 2010.
Myers, G. Editor (© 2009). Emerging CV Risk Factors. The National Academy of Clinical Biochemistry, Laboratory Medicine Practice Guidelines, Emerging Biomarkers for Primary Prevention of Cardiovascular Disease and Stroke [On-line information]. Available online at http://www.aacc.org/members/nacb/LMPG/OnlineGuide/PublishedGuidelines/risk/Pages/default.aspx through http://www.aacc.org. Accessed September 2010.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 110-114.
Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pp 254.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 678-681.
Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, Pp 202-203.
Jill Rubin, Thomas A. Pearson, Roberta G. Reed, and Lars Berglund. Fluorescence-based, Nonradioactive Method for Efficient Detection of the Pentanucleotide Repeat (TTTTA)n Polymorphism in the Apolipoprotein(a) Gene. Clinical Chemistry Oct 2001; 47: 1758 - 1762.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Spengler, R. (2002 May 14, Updated). What is lipoprotein(a)? St. Joseph Health System, Health Library [On-line information]. Available online at http://www.sjo.org/library/healthguide/MedicalTests/topic.asp?hwid=tv6799abc through http://www.sjo.org.
Paxton, A. (2002 July). One Year Later, Cholesterol Guidelines Sinking In. In the News, CAP Today Feature Story [On-line article]. Available online at http://www.cap.org/captoday/archive/2002/cholesterol_guidelines_feature.html through http://www.cap.org.
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Sih, I, Contributor. Chapter 63. Lipoprotein Disorders. The Merck Manual of Geriatrics, Section 8: Metabolic and Endocrine Disorders [On-line information]. Available online at http://www.merck.com/pubs/mm_geriatrics/sec8/ch63.htm through http://www.merck.com.
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Stewart, C. (2001 February 8). Lecture 6: Cholesterol and Lipoproteins. Lecture notes, Biol 366, Univ at Albany, NY [On-line lecture]. PDF available for download at http://www.albany.edu/faculty/cs812/bio366/L06_lipoproteins.pdf through http://www.albany.edu/.
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Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO., Pp 110-114.
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(September 2006) High Lipoprotein(a) Levels Plus High LDL Increases CVD Risk in Women. Nainggolan L. Medscape Medical News (online information, accessed August 2007). Available online at http://www.medscape.com/viewarticle/544893 through http://www.medscape.com.
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