Antiphospholipid Syndrome


Antiphospholipid Syndrome (APS) is a blood disorder caused by abnormal proteins (antibodies) in the blood that lead to an increase risk of blood clotting and problems with pregnancy.

APS is diagnosed in people who have blood clots or problems with pregnancy AND who have evidence of these abnormal antibodies in the blood.

What are antibodies?

Antibodies are proteins that are normally produced by the immune system to fight infections. The immune system produces different antibodies for different infections. APS occurs when antibodies are produced by the immune system that are directed against the body rather than infections; it is therefore called an auto(self)immune disorder.

How do you measure antibodies for APS?

Antibodies in APS are measured using a blood test.

There are three blood tests we use:

  1. Lupus Anticoagulant (LAC)
  2. Anticardiolipin Antibody (ACLA)
  3. Beta 2 Glycoprotein 1 (B2GP1)

It is important to remember that not everybody who has these antibodies in the blood will develop blood clots or have problems with pregnancy; some people have these antibodies but never develop any problems with blood clots. Sometimes these antibodies occur after an infection and then disappear.

How did I get APS?

We are not sure why APS develops. It is more common in females than males.

What are the main problems with having APS?

The main problems with having APS is being at risk of having a blood clot and getting (or staying) pregnant.

Blood clots can occur anywhere in the body; often the veins in the leg, sometimes in the arteries of the body and sometimes APS can even cause strokes.

APS is associated with recurrent miscarriages and other complications of pregnancy.

What is the treatment for APS?

If you have APS it is likely you will need blood thinning mediation (anticoagulation or anti-platelet therapy) to reduce the risk of having a blood clot or to manage recurrent miscarriages. Blood thinning works by stopping the blood clotting system working properly and prevents blood clots in patients with APS. A number of studies have suggested anti-platelet therapy (aspirin) and anticoagulation can help in patients with APS and problems with pregnancy.

How long will I have to be on blood thinning for?

Unfortunately, you are at a high risk of having another blood clot if you have already had one blood clot and have blood tests showing you have APS. Blood thinning will reduce this risk significantly – current recommendations suggest that you should stay on blood thinning as long as the risk of blood thinning (bleeding) do not outweigh the benefits. You should talk about continuing blood thinning with your doctor.

Resources used to produce this information sheet.

  1. Rand, H The Antiphospholipid Syndrome. Haematology 2007 pp 136 – 142
  2. Garda, DA Khamashata, MA Crowther MA. How we diagnose and treat thrombotic manifestations of the Antiphospholipid syndrome; a case based review. Blood 2007 pp 3122 – 3127

Updated: May 2018


The information presented in this fact sheet is intended as a general guide only. Patients should seek further advice and information about Antiphospholipid Syndrome and or their individual condition from their treating haematologist or doctor.

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