Lab Testing Related to Antiphospholipid Syndrome

Antiphospholipid Syndrome is also known as APS. This autoimmune disorder is a condition where the human body’s very own immune system produces proteins called antibodies. These antibodies mistakenly attack the tissues and cells of their own host body. APS is known to increase risks of inappropriate formations of blood clots, meaning it’s deemed an excessive clotting disorder or thrombophilia. 

Antibodies are normally a line of defense for the body against any infections. However, with APS, antibodies go out and attack the lipid-proteins present in cell membranes and platelets. These autoantibodies wind up interfering with the process of blood clotting in a manner that, as of the time of writing, is still not understood. APS relates to several conditions, including thrombotic episodes (blood clots), thrombocytopenia (low platelet numbers), and complications with pregnancy, such as recurrent miscarriages and pre-eclampsia. 

Several primary antiphospholipid antibodies are associated with the condition of Antiphospholipid Syndrome. They include the following: 

  • β2GP1 or beta-2 glycoprotein antibody 
  • Cardiolipin antibody 
  • Lupus anticoagulant 

These antibodies increase the risk of someone developing recurrent and inappropriate blood clots in arteries and veins alike. Individuals who have APS might experience one or even multiple blood clots. Complications and symptoms might range from minor to major. 

If a blood clot forms, it can obstruct the flow of blood, resulting in tissue and organ damage. 

If blood clots travel to the heart, lungs, kidneys, or brain, then they can trigger kidney damage, a stroke, a heart attack, and/or a pulmonary embolism. 

Among those with Antiphospholipid Syndrome, a small subset might have a widely spread thrombotic disease known as ‘catastrophic’ APS because of the damage that occurs with many of the bigger internal organs of the human body. 

APS can impact anyone, but those who have lupus and women of potential child-bearing age are two groups afflicted more often than others. Antiphospholipid antibodies are discovered routinely in anywhere from 1 up to 5 percent of a healthy population of general people. APS has an incidence rate of approximately 5 cases among every 100,000 people each year, with a reported prevalence of 40 to 50 cases for every 100,000 people. This is the most frequent reason for strokes in the population segment under 50 years of age. Twenty percent of women experiencing recurrent miscarriages are afflicted with APS. 

Those persons who have antiphospholipid antibodies might have multiple antibodies present without any associated symptoms, but they might also have APS at the same time they have a concurrent autoimmune disorder, like lupus. Low antiphospholipid antibody levels can also be associated with Lyme disease, HIV, and certain cancers. APS is also seen temporarily during some infections, in the elderly, and with certain medications. These medications include the antibiotic amoxicillin, psychiatric drugs like phenothiazines, and procainamide, the hearth rhythm regulator. If someone has a family member already known to have APS, that can potentially increase the person’s risk. 


Thrombosis or a blood clot forming inside a blood vessel is sometimes the first apparent sign resulting in a diagnosis of APS. Two other possibilities include recurrent pregnancy loss or thromboembolism, where a clot gets in the way of blood flow to one of the vital organs, like lungs or the human brain. 

Women who have Antiphospholipid Syndrome and get pregnant are at heightened risk for various complications, including loss of the pregnancy through miscarriage, premature childbirth, placenta underdevelopment, pre-eclampsia, and deep vein thrombosis. However, they might not experience any symptoms or signs of this condition in advance of getting pregnant. 

Health issues frequently associated with the condition of APS might include any of the following: 

  • Hypertension, or high blood pressure 
  • DVT or deep vein thrombosis is the formation of blood clots down in the legs before they move up into the lungs where they can trigger a pulmonary embolism that is possibly life-threatening 
  • Strokes 
  • TIAs, also known as transient ischemic attacks or just ‘mini-strokes,’ which happen when the blood flow to the brain is temporarily disrupted 
  • Heart attack or angina, which is chest pain resulting from a reduction in blood flow into the human heart 
  • Skin conditions that are related to clot formation in blood vessels supplying the skin, including necrosis or death of the skin tissue, skin ulcers, and livedo reticularis 
  • Nasal or gum bleeding due to thrombocytopenia, a low count of platelets 
  • Less common symptoms and signs can include the following possibilities, among others: 
  • Heart valve issues 
  • Visual disturbances or loss of vision 
  • Repetitive migraines or headaches 
  • Mobility and balance problems 
  • Difficulty in thinking clearly or concentrating 

Laboratory Criteria

Testing goals include the diagnosis of Antiphospholipid Syndrome and distinguishing it from any other sources of complications and symptoms. Not all who have antiphospholipid antibodies winds up having complications and/or symptoms. 

A positive test for one of the various autoantibodies on at least two occasions a minimum of three months apart: 

  • Lupus anticoagulant: must be present, per the International Society on Thrombosis and Hemostasis guidelines 
  • Anticardiolipin antibody: must be present at either a medium or even high level. 
  • Beta-2-Glycoprotein 1 antibody: must be present at a very high level, as the testing laboratory must establish it as being over the 99th normal percentile 

Laboratory Testing 

Blood testing can be useful in the detection of autoantibody presence. These tests include: 

Lupus anticoagulant testing (for example, DRVVT & hexagonal phase phospholipid neutralization test or dilute Russell viper venom test) 

Cardiolipin antibodies 

Beta-2-Glycoprotein 1 antibodies 

Other tests might be ordered for the evaluation of blood cells and clotting. These might include: 

PTT: Partial thromboplastin time 

PT: Prothrombin time 

CBC: Complete blood count for evaluating platelets and blood cells. 

Other additional tests for evaluating other potential causes of symptoms, like a 1:1 Mix study (dilute PTT) for screening the blood for lupus anticoagulant.