At a Glance
Why Get Tested?
To help evaluate a prolonged partial thromboplastin time (PTT) and/or a thrombotic episode, to help determine the cause of recurrent miscarriages, and as part of an evaluation for antiphospholipid syndrome; the tests are not used to diagnose systemic lupus erythematosus (SLE)
When to Get Tested?
A blood sample obtained by inserting a needle into a vein in the arm
Test Preparation Needed?
The Test Sample
What is being tested?
The lupus anticoagulants (LA) are autoantibodies, produced by a person's immune system against their own phospholipids and/or phospholipid-associated proteins. Phospholipids play a vital role in the blood clotting process. They are found on the surface of platelets and assist in the activation of several coagulation factors, which are proteins that are sequentially activated in response to blood vessel or tissue damage and bleeding in a process called hemostasis. Lupus anticoagulants were so named because they were first found among patients with systemic lupus erythematosus (SLE), although they may also occur with increased frequency in individuals with other autoimmune diseases, infections such as HIV/AIDS, inflammation, cancers, and in those who are taking certain medications, such as phenothiazines, procainamide, and fansidar. The antibodies are present in about 1-2% of the general population and may develop in people with no known risk factors.
In the body, lupus anticoagulants increase the risk of developing blood clots in both the veins and arteries, often in the veins in the legs (deep vein thrombosis). These clots may block blood flow in any part of the body, leading to stroke, heart attack, pulmonary embolism, as well as recurrent miscarriages, especially in the second and third trimesters. In laboratory testing, lupus anticoagulants cause prolongation in the clotting times (e.g., PTT) by binding phospholipids or phospholipid-associated proteins, which are necessary components of coagulation reactions (For more on this, see the explanation of the coagulation cascade). Importantly, lupus anticoagulants do not cause bleeding in the body.
There is no single test for the detection of lupus anticoagulant. The presence of LA is usually determined by using a panel of sequential tests. Initial testing typically involves one or more tests that depend on phospholipid reagents, usually PTT, the LA-sensitive PTT (PTT-LA) or Dilute Russell viper venom test (DRVVT). If lupus anticoagulant is present in a person's sample of blood, it binds to the assay's phospholipids, preventing them from participating in the coagulation reaction and therefore prolonging the clotting time results. Depending on the results of these initial tests, certain follow-up tests are performed to either confirm or exclude the presence of lupus anticoagulant. For more on this, see the section titled "What does the test result mean?"
The lupus anticoagulant is one of three primary antiphospholipid antibodies that are associated with an increased risk of thrombosis. The others are cardiolipin antibodies and antibodies against beta2 glycoprotein 1 (anti-beta2-GPI, less common). Patients with antiphospholipid syndrome (also called Hughes syndrome) have one or more of these antibodies detectable in their blood. Each antibody interferes with the clotting process in a way that is not yet well understood. Singly and together, they increase a person's tendency to clot inappropriately, causing thrombosis and/or thromboembolism.
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.
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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
(© 2010). Antiphospholipid Antibodies. Lupus Foundation of America [On-line information]. Available online at http://www.lupus.org/webmodules/webarticlesnet/templates/new_aboutaffects.aspx?articleid=82&zoneid=17 through http://www.lupus.org. Accessed August 2010.
Belilos, E. and Carsons, S. (Updated 2009 August 3). Antiphospholipid Syndrome. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/333221-overview through http://emedicine.medscape.com. Accessed August 2010.
Berg, T. (2009 December 1). Antiphospholipid Antibody Syndrome and Pregnancy. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/261691-overview through http://emedicine.medscape.com. Accessed August 2010.
Gersten, T. (Updated 2009 January 1). Lupus anticoagulants. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000547.htm. Accessed August 2010.
Rodgers, III, G. et. al. (Updated 2010 August). Antiphospholipid Syndrome – APS. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/APS.html?client_ID=LTD through http://www.arupconsult.com. Accessed August 2010.
Mayo Clinic Staff (2009 April 4). Antiphospholipid syndrome. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/antiphospholipid-syndrome/DS00921 through http://www.mayoclinic.com. Accessed August 2010.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 70-71.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 692-693.
Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. McPherson R, Pincus M, eds. Philadelphia, PA: Saunders Elsevier: 2007, Pp 774-775.
The Fritsma Factor: Summary of ISTH SSC 2009 Updated Guidelines for Lupus Anticoagulant Detection (October 2009). Available online at http://www.fritsmafactor.com/newfritsmafactor/?p=1947 through http://www.fritsmafactor.com. Accessed November 2010.
Devreese K, Hoylaerts M. Challenges in the Diagnosis of the Antiphospholipid Syndrome. Clinical Chemistry 56: 930-940, 2010. Available at http://www.clinchem.org/cgi/content/full/56/6/930 through http://www.clinchem.org. Accessed November 2010.
Pengo V, et.al Update of the guidelines for lupus anticoagulant detection. Journal of Thrombosis and Hemostasis, Vol. 7, issue 10 Pp. 1737-1740, October 2009. Available online at http://onlinelibrary.wiley.com/doi/10.1111/j.1538-7836.2009.03555.x/full through http://onlinelibrary.wiley.com. Accessed November 2010.
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.
Castellone, D. (2001 January 8). The Lupus Anticoagulant: Truth or Consequence. Advance Newsmagazines [On-line Newsletter]. Available online at http://www.advanceforal.com/common/editorial/editorial.aspx?CC=4712 through http://www.advanceforal.com.
(2002 November 19, Updated). Antiphospholipid Antibody. Mass Gen. Hospital Pathology Service Laboratory Medicine [On-line information]. Available online at http://www.mgh.harvard.edu/labmed/lab/coag/handbook/co003100.htm#co003100 through http://www.mgh.harvard.edu.
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(© 2007). Lupus Anticoagulant Panel with Reflex to 1:1 Mixes & Confirmations. ARUP's Laboratory Test Directory [On-line information]. Available online at http://www.aruplab.com/guides/ug/tests/0030181.jsp through http://www.aruplab.com. Accessed on 3/25/07.
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