Antiphospholipid Antibodies

Also known as: APA

Formal name: Antiphospholipid Antibodies

Related tests: Lupus Anticoagulant Testing, Cardiolipin Antibodies, PTT (partial thromboplastin time), Russell viper venom time (RVVT), Platelet neutralization procedure, Kaolin clotting time, Hexagonal phospholipid confirmatory test, Dilute prothrombin time, Anti-beta2 glycoprotein I antibodies, Anti-phosphatidylserine antibodies, Anti-prothrombin antibodies

At a Glance

Why Get Tested?

To help investigate inappropriate clot formation; to help determine the cause of recurrent miscarriage; to evaluate a prolonged PTT (partial thromboplastin time); as part of an evaluation for antiphospholipid antibody syndrome

When to Get Tested?

When you have a prolonged PTT test; when you have had recurrent unexplained venous or arterial blood clots; when you have had recurrent miscarriages, especially in the second and third trimesters

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Antiphospholipid antibody tests are used to detect several specific phospholipid-binding proteins that the body produces against itself in an autoimmune response to phospholipids. Found in cell membranes and platelets, phospholipids are a normal part of the body. They are lipid molecules that play a crucial role in blood clotting. When antiphospholipid antibodies are produced, they interfere with the clotting process in a way that is not fully understood. They increase an affected patient’s risk of developing recurrent inappropriate blood clots (thrombi) in arteries and veins, which can lead to strokes and heart attacks. Antiphospholipid antibodies are also associated with thrombocytopenia and with the risk of recurrent miscarriages (especially in the 2nd and 3rd trimester), premature labor, and preeclampsia.

One or more antiphospholipid antibodies are frequently seen with autoimmune disorders such as Systemic Lupus Erythematosus (SLE). They may also be seen with HIV, some cancers, in the elderly and temporarily with infections and with some drug treatments (such as phenothiazines and procainamide).

Antiphospholipid syndrome (APS), also called Hughes syndrome, is a recognized group of signs and symptoms that includes the formation of thrombi, miscarriages, thrombocytopenia, and the presence of one or more antiphospholipid antibodies. APS can be primary (with no underlying autoimmune disorder) or secondary (existing with a diagnosed autoimmune disorder).

The most common antiphospholipid antibodies are cardiolipin antibodies (also called anticardiolipin antibodies) and the lupus anticoagulant. Others that are not as frequently tested include anti-beta2 glycoprotein I and anti-phosphatidylserine. There are two types of tests that are used to detect antiphospholipid antibodies. The first is the test for cardiolipin antibodies used to detect several classes (IgG, IgM, and/or IgA) of the antibodies themselves. The second type is lupus anticoagulant assays, which are functional tests used to detect whether the antibody can block phospholipid-dependent tests. These are tests that measure the time it takes for a patient’s sample to clot, and they require the presence and action of phosopholipids for clotting to occur. Lupus anticoagulant assays begin with an assay to detect prolongation of a phospholipid dependent test, the most common of which is the PTT. Confirmatory studies then need to be performed, preferably with a similar method as the initial screening assay.

Additional diagnostic and confirmatory tests may include RVVT (Russell viper venom time), PNP (platelet neutralization procedure), KCT (kaolin clotting time) and/or hexagonal lipid neutralization test.

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.

The Test

How is it used?

Antiphospholipid testing is used to help determine the cause of an unexplained thrombotic episode, recurrent fetal loss, thrombocytopenia, and/or a prolonged PTT test. Depending on the patient’s clinical findings, a physician may order one or more types and classes of these tests to help detect the presence of antiphospholipid antibodies and to help diagnose antiphospholipid syndrome (APS). Cardiolipin antibodies (IgG, IgM, and sometimes IgA) are frequently ordered as they are the most common antiphospholipids. If a patient has a prolonged PTT test, further lupus anticoagulant testing is usually indicated. Anti-beta2 glycoprotein I and anti-phosphatidylserine testing may be ordered along with the other antiphospholipid antibodies to detect their presence and to provide the doctor with additional information.

If an antiphospholipid antibody is detected, the same test(s) may be ordered 8 to 10 weeks later to determine whether their presence is persistent or temporary. If a patient with an autoimmune disorder tests negative for antiphospholipid antibodies, he may be retested as these antibodies may develop at any time.

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When is it ordered?

Antiphospholipid antibody testing may be ordered when a patient has symptoms suggestive of a thrombotic episode, such as pain and swelling in the extremities, shortness of breath, and headaches. It also may be ordered when a woman has had recurrent miscarriages and/or as a follow-up to a prolonged PTT test. When one of the tests is positive, it may be repeated several weeks later to determine whether the antibody is temporary or persistent. Antiphospholipid testing may be done when clinical signs suggest the presence of antiphospholipid syndrome. When a patient with an autoimmune disorder tests negative for antiphospholipid antibodies, one or more of the tests may be ordered in the future to screen for the development of an antiphospholipid antibody.

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What does the test result mean?

Care must be taken when interpreting the results of antiphospholipid antibody tests. A negative result means only that the specific antibody tested was not present at the time of the test. Low to moderate levels of one or more antibodies may occur temporarily due to an infection or drug or may appear as a person ages. These concentrations are often not considered significant but must be examined in conjunction with a patient’s symptoms and other clinical information. In some cases, a person may have one or more classes of a specific antibody present or absent. For instance, they may have significant quantities of IgG and IgM cardiolipin antibodies or they may only be positive for the less frequently tested IgA cardiolipin antibody. Moderate to high levels of one or more antiphospholipid antibodies, which persist when tested again 8 to 10 weeks later, indicate the likely continued presence of that specific antibody.

If the tests indicate the presence of the lupus anticoagulant and it persists when retested, then it is likely that the patient is positive for the lupus anticoagulant. Patients who have one or more antiphospholipid antibodies and those that are diagnosed with antiphospholipid syndrome have an increased risk of having recurrent thrombotic episodes, recurrent miscarriages, and thrombocytopenia. Test results cannot predict, however, the likelihood of complications, the type, or the severity in a particular patient. Some will have a variety of recurrent problems while others may never experience any difficulties. Examples of this include an asymptomatic patient who is diagnosed with antiphospholipid antibodies following a prolonged PTT test that is done for another reason (such as a pre-surgical screen) and an asymptomatic elderly person who has acquired an antiphospholipid antibody.

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Is there anything else I should know?

Occasionally, antiphospholipid testing may be ordered to help determine the cause of a positive VDRL/RPR test for syphilis. The reagents used to test for syphilis contain phospholipids and can cause a false positive result in patients with antiphospholipid antibodies.

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Common Questions

1. Is there anything I can do to prevent or get rid of antiphospholipid antibodies?

No. The process that causes them to be produced is not well understood. There are controllable risk factors, however, such as smoking and obesity that also increase your risk of clotting. Addressing these issues may help to lower your overall risk of developing thrombi.

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2. If I have one antiphospholipid antibody, will I develop others?

It is possible, but there is no way to predict when or if this will happen. Antiphospholipid antibody development, and the development of symptoms and complications, depends on the individual.

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Article Sources

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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

Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 134-135.

National Institute of Neurological Disorders and Stroke. NINDS Antiphospholipid Syndrome Information Page. [On-line information. 2007 February 08, Updated.]. Available online at http://www.ninds.nih.gov/disorders/antiphosphlipid/antiphospholipid.htm through http://www.ninds.nih.gov. Accessed on 4/12/08.

American Heart Association. Antiphospholipid Syndrome (APLS). [On-line information. © 2008).]. Available online at http://www.americanheart.org/presenter.jhtml?identifier=4459 through http://www.americanheart.org. Accessed on 4/12/08.

Belilos, E. and Carsons, S. Antiphospholipid Syndrome. eMedicine [On-line information. 2007 August 10, Updated.]. Available online at http://www.emedicine.com/med/topic2923.htm through http://www.emedicine.com. Accessed on 4/12/08.

Lupus Foundation of America. Antiphospholipid Antibodies. [On-line information. © 2008.]. Available online at http://www.lupus.org/webmodules/webarticlesnet/templates/new_aboutaffects.aspx?articleid=82&zoneid=17 through http://www.lupus.org. Accessed on 4/12/08.

APS Foundation of America. Antiphospholipid Antibody Syndrome. [On-line information. 2006 October 15, Revised.]. Available online at http://www.apsfa.org/aps.htm through http://www.apsfa.org. Accessed on 4/19/08.

ARUP Consult. Antiphospholipid Syndrome – APS. [On-line information. © 2006-2008.]. Available online at http://www.arupconsult.com/Topics/HematologicDz/APS.html# through http://www.arupconsult.com. Accessed on 4/19/08.

National Human Genome Research Institute. Learning About Antiphospholipid Syndrome (APS). [On-line information. 2008 February 5, Reviewed. ]. Available online at http://www.genome.gov/17516396 through http://www.genome.gov. Accessed on 4/20/08.

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.

(2001 June 26). Antiphospholipid Antibody Syndrome. Hematology Resource Page, Patient Resources University of Illinois - Urbana/Champaign, Carle Cancer Center [On-line information]. Available online at http://www-admin.med.uiuc.edu/hematology/PtAPS.htm through http://www-admin.med.uiuc.edu.

(© 2004). Antiphospholipid Testing. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_al67.jsp#3965115 through http://www.arup-lab.com.

(© 2004). Beta-2 Glycoprotein, Antibody. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_al95.jsp#1145254 through http://www.arup-lab.com.

(© 2004). Cardiolipin Antibodies, IgG and IgM. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_a133.jsp#1059158 through http://www.arup-lab.com.

Lupus Anticoagulant Panel with Reflex to 1:1 Mixes and Confirmations. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.arup-lab.com/guides/clt/tests/clt_a52b.jsp#1141319 through http://www.arup-lab.com.

Zepf, B. (2002 June 1). A Discussion of the Antiphospholipid Syndrome. American Family Physician, Tips from other Journals, [From Levine JS, et al. The antiphospholipid syndrome. N Engl J Med March 7, 2002;346:752-63] [On-line journal]. Available online at http://www.aafp.org/afp/20020601/tips/11.html through http://www.aafp.org.

Petri, M. (2001). Antiphospholipid Antibodies: Anticardiolipin Antibodies and the Lupus Anticoagulant in Systemic Lupus Erythematosus. The Lupus Foundation of America [On-line information]. Available online at http://www.lupus.org/education/brochures/antiphos02.html through http://www.lupus.org.

Solenski, N. (2004 April 1). Transient Ischemic Attacks: Part I. Diagnosis and Evaluation. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20040401/1665.html through http://www.aafp.org.

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(2001). Antiphospholipid Antibody. Massachusetts General Hospital, Laboratory Medicine, Coag Test Handbood Index [On-line information From: Elizabeth M. Van Cott, M.D., and Michael Laposata, M.D., Ph.D., "Coagulation." In: Jacobs DS et al, ed. The Laboratory Test Handbook, 5th Edition. Lexi-Comp, Cleveland, 2001; 327-358.]. Available online at http://www.mgh.harvard.edu/labmed/lab/coag/handbook/CO003100.htm through http://www.mgh.harvard.edu.

De Moerloose P Antiphospholipid antibodies: do we still need to perform anticardiolipin assays? J Thromb Haemost 2004; 2:1071-1073 and Nash MJ et al.

The anticardiolipin assay is required for sensitive screening for antiphospholipid antibodies. J Thromb Haemost 2004; 2:1077-1081.

Brandt J et al. Criteria fort the diagnosis of Lupus anticoagulants: an update on behalf of the subcommittee on Lupus Antiocoagulant/Antiphospholipids Antibody of the Scientific and Standardization Committee of the ISTH. Thromb Haemost 1995:74:1185-1190.