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Antiphospholipid Syndrome Terminology – Top 10 Series

Top 10 Questions to Clarify Terminology Used in Antiphospholipid Syndrome Discussions

By Doruk Erkan, MD, MPHOmer Uludag

1. What are the commonly used abbreviations in antiphospholipid syndrome?

Ab: antibody
aGPI or2GPI: anti-Beta-2-glycoprotein-I antibody
Ag: antigen
aCL: anticardiolipin antibody
aPL: antiphospholipid antibody
APS: antiphospholipid syndrome
aPTT: activated partial thromboplastin time
ASA: aspirin
CAPS: catastrophic antiphospholipid syndrome
CT: computed tomography
dRVVT: dilute Russell’s viper venom
DVT: deep vein thrombosis
ELISA: enzyme-linked immunosorbent assay
HCQ: hydroxychloroquine (Plaquenil®)
Ig: immunoglobulin
INR: international normalized ratio
IVIG: intravenous immunoglobulin
LA: lupus anticoagulant
LMWH: low molecular weight heparin
MI: myocardial infarction
MRI: magnetic resonance imaging
PE: pulmonary embolism
PT: prothrombin time
PTT: partial thromboplastin time
SLE: systemic lupus erythematosus
TIA: transient ischemic attack
USG: ultrasound
VDRL: venereal disease research laboratory

2. What general terms should patients know about antiphospholipid antibodies?

antibody: A large protein produced by the immune system to destroy foreign substances such as bacteria, viruses, or chemical toxins.

autoantibody: An abnormal antibody that attacks the patient’s own tissues and organs; present in autoimmune disease.

antiphospholipid antibody: An autoantibody that acts against phospholipid (see below) binding plasma proteins, thereby increasing the risk of blood clotting.

lymphocytes: Lymphocytes are the white blood cells responsible for the immune response. There are two major classes of lymphocytes: T cells and B cells. Both cells are involved in immune response; B cells develop within the bone marrow and become either antibody- or autoantibody-producing cells.

β2-glycoprotein-I: The major phospholipid (see below) binding plasma protein that is targeted by antiphospholipid antibodies.

inflammation: Local response (increased blood flow and movement of immune cells) characterized by pain, redness, heat, and swelling.

phospholipids: Fatty molecules that are the major component of cell membranes and other cellular compartments.

3. What terms should patients know about the effects of antiphospholipid antibodies on blood clotting?

embolus: A blood clot that travels from the original site to another site in the body. An embolus can decrease or block blood flow (ischemia – see below), depriving tissues of oxygen delivery. (Plural: Emboli)

deep vein thrombosis (DVT): A blood clot in the vein of an extremity (especially in the leg), which can result in swelling, redness, and pain.

infarction: Tissue death due to obstruction of the blood supply (ischemia). The most common causes are blood clots or emboli.

ischemia: Restriction of the blood supply to tissues or organ systems resulting in insufficient oxygen and nutrition delivery.

microthrombus: Small sized thrombus (see below), which primarily blocks small- sized vessels (e.g., those found in the kidneys).

myocardial infarction: Damage or death of the heart muscle due to decreased blood flow (ischemia) for a prolonged time (also known as a “heart attack”).

perfusion: Delivery of blood to the tissues.

pulmonary embolism: A blood clot in a deep vein that breaks off and travels through the blood to an artery in the lungs (Note: blood clots in the thighs are more likely to cause pulmonary embolism than are blood clots in the lower parts of the legs or other parts of the body).

superficial vein thrombosis (phlebitis): Blood clot formation in the veins that are close to the skin’s surface. Unlike deep vein thrombosis (DVT), there is no risk of pulmonary emboli with superficial vein thrombosis.

thrombus: A blood clot that forms in a vessel, which can partially or completely block blood flow into the tissues; depending on the degree of blockage, a thrombus can cause damage or death of the tissues (Plural: Thrombi).

transient Ischemic Attack (TIA): Symptoms similar to a stroke (e.g., sensory loss, numbness, weakness, or visual disturbances) that occur due to decreased blood flow (ischemia) to a specific location in the brain for a short period of time. A TIA may last for up to 24 hours, but in most cases lasts for only a few hours.

4. What terms should patients know about the effects of antiphospholipid antibodies on pregnancy?

eclampsia: A severe form of preeclampsia (see below) that can also cause seizures and coma in the mother.

embryonic loss: Miscarriage between the fifth and tenth weeks of pregnancy.

fetal loss: Miscarriage after the tenth week of pregnancy.

miscarriage: Spontaneous termination of the pregnancy resulting in loss of the fetus before the 20th week of pregnancy. Also called Spontaneous Abortion.

preeclampsia: Sudden increase in blood pressure and increased urine protein excretion after the 20th week of pregnancy.

pre-embryonic loss: Miscarriage within the first four weeks of pregnancy.

postpartum period: Time between the delivery of the infant and the return of the reproductive organs to their pre-pregnancy state. The postpartum period usually lasts five to seven weeks.

5. What terms should patients know about other manifestations of antiphospholipid syndrome?

anemia: Low red blood cell or hemoglobin counts. (Hemoglobin is the oxygen-carrying pigment within the red blood cells.)

autoimmune hemolytic anemia: Anemia that occurs when autoantibodies attack and destroy the red blood cells.

cognition: Awareness of self and environment through brain activity including perception, memory, and thought.

livedo reticularis: Purplish discoloration of the skin due to swelling of the veins under the skin (it is the most common skin manifestation of Antiphospholipid Syndrome and is primarily seen on the knees, thighs, and arms).

nephropathy: Kidney disease, which can be caused by external causes (e.g., infections) or internal abnormalities (e.g. microthrombosis, attack of inflammatory cells on the kidney tissue).

proteinuria: Excessive protein excretion in urine, which can occur in patients with antiphospholipid antibody-related nephropathy.

thrombocytopenia: Platelet (blood cells involved in blood clotting) count that is lower than the normal limit, which is between 150,000-450,000 platelets per microliter of blood.

vegetation: Abnormal growths – small masses or blood clots – on the heart valves.

6. What tests are commonly used to diagnose antiphospholipid syndrome?

anticardiolipin antibody test: One of three main blood tests that detects antiphospholipid antibodies using an ELISA method (see below).

anti β2-glycoprotein-I antibody test: One of three main blood tests that detects antiphospholipid antibodies using an ELISA method (see below).

ELISA: A diagnostic enzyme-linked immunosorbent assay that detects specific autoantibodies in the blood sample.

lupus anticoagulant (LA) test: One of three main blood tests that detects antiphospholipid antibodies using a functional clotting assay. The LA test is typically performed in three steps:

  • screening test (e.g., aPTT or dRVVT):
    • Measures the duration of clotting in a laboratory (the screening tests are prolonged in patients with antiphospholipid antibodies).
  • mixing test:
    • Rules out coagulation factor deficiencies by mixing the patient’s blood sample with an equal amount of blood taken from a healthy individual.
  • confirmatory test:
    • Confirms the presence of antiphospholipid antibodies as demonstrated in the screening test (above) with the addition of extra phospholipids. Normalization of the prolonged screening tests confirms the presence of antiphospholipid antibodies.

VDRL test: Screening test for syphilis, which can produce a false positive in patients with antiphospholipid antibodies. Of note, the VDRL test is not part of the classification criteria for antiphospholipid syndrome.

7. What terms should patients know with regard to the prevention of diseases?

primary prevention: Preventive actions taken prior to the onset of disease and reduce the possibility of disease occurrence. For example, prevention of the first blood clot in a patient with positive antiphospholipid antibodies.

secondary prevention: Preventive actions taken to stop the progression of a disease at the early stages. For example, prevention of blood clots in antiphospholipid antibody-positive patients who had previous blood clots.

tertiary prevention: Preventive actions targeted to reduce or limit impairment and disability, and to enhance the patient’s quality of life after disease symptoms develop. For example, medical therapy to prevent further effects of recently formed lung emboli.

8. What general terms should patients know about antiphospholipid syndrome treatment?

anticoagulant drugs: Medications that prevent coagulation (clotting ability of the blood). Commonly used anticoagulant drugs are heparin and warfarin (Coumadin®).

anti-inflammatory drugs: Medications that block the release of molecules responsible for inflammation.

antiplatelet drugs: Medications that prevent clotting by blocking molecules that trigger accumulation of platelets (blood cells responsible for clotting). The most commonly used antiplatelet drug is aspirin.

international normalized ratio (INR): The ratio between clotting time of the patient’s blood sample and normal clotting time in blood drawn from healthy individuals. The INR test is used to monitor warfarin therapy.

immunosuppressive drugs: Medications that suppress immune system function.

thrombolytic drugs: Medications used to dissolve blood clots in conditions such as myocardial infarction.

9. What are some of the medications commonly used in the treatment of antiphospholipid syndrome?

aspirin: A medication with antiplatelet effects at low doses.

corticosteroid (e.g., prednisone): A medication with multiple effects including metabolic, anti-inflammatory, and immunosuppressive actions. Corticosteroids are mostly used in Catastrophic Antiphospholipid Syndrome.

heparin: Anticoagulant agent used mainly in acute thrombosis and during pregnancies of antiphospholipid antibody-positive patients. It is given intravenously (in the vein) or as an injection under the skin.

hydroxychloroquine (Plaquenil®): An antimalarial drug (used in the prevention and treatment of malaria) with anti-inflammatory and antithrombotic effects. It may also reduce the clotting risk in antiphospholipid antibody positive patients.

intravenous immunoglobulin (IVIG): Antibodies obtained from donor plasma; the medication is used intravenously to block inflammation. IVIG is mostly used in Catastrophic Antiphospholipid Syndrome.

statins: Cholesterol-lowering agents with anti-inflammatory effects. Statins may reduce aPL binding to the arteries and veins.

warfarin (Coumadin®): Anticoagulant pill used to prevent recurrence of blood clots.

10. What is APS ACTION?

APS ACTION (Antiphospholipid Syndrome Alliance for Clinical Trials and International Networking) is an international organization formed in November 2010. The goal of APS ACTION is to support clinical trials and ultimately advance the understanding and treatment of APS. More information about APS ACTION can be obtained at


Doruk Erkan, MD, MPH
Attending Rheumatologist, Hospital for Special Surgery
Professor of Medicine, Weill Cornell Medical College

Omer Uludag
Visiting Medical Student, Hacettepe University, School of Medicine, Ankara, Turkey

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References and Further Information:

Thrombus. Accessed on 10/12/2012

Erkan D, Lally L, Lockshin MD.  “What Should Patients Know About Antiphospholipid Antibodies and Antiphospholipid Syndrome?”.  In: Antiphospholipid Syndrome: Insights and Highlights from the 13th International Congress on Antiphospholipid Antibodies, 1st Edition. Eds: Erkan and Pierangeli, Springer, 2012;295-309.

Leavell HR, Clark EG. Preventive Medicine for the Doctor in His Community, 3rd edition. New York: McGraw-Hill Book Company, 1965.

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