Frequently Asked Questions



APS is described as an autoimmune condition – what does autoimmune mean?

The immune system is designed to protect and defend the body from a whole host of foreign invaders such as bacteria, viruses and parasites.

However, in some cases, the body gets confused and starts making antibodies against itself. As the word ‘auto’ means self, the term autoimmune is used to describe disorders where the immune system turns on itself.


What are antiphospholipid antibodies?

Antibodies are proteins in the blood which help defend the body against foreign invaders.

Antiphospholipid antibodies (aPL) are harmful antibodies that attack proteins and fats called phospholipids in blood cells. Due to the phospholipids being attacked by the aPL, the blood becomes excessively 'sticky', resulting in a higher risk of clotting.


Where do the antiphospholipid antibodies come from?

The simple answer is: we don’t know and won’t until much more research has been carried out.

People can have antiphospholipid antibodies (aPL) and not have APS – they will often occur briefly in patients with certain cancers, drugs and infections, which is why it is important to have two sets of tests at least six weeks apart.


Why have I developed APS?

Again, we are not sure why the immune system becomes over-active and produces the antiphospholipid antibodies (aPL). Still, there is increasing evidence that there is probably a genetic tendency that, when triggered by an external factor, activates the syndrome.

It is currently thought that triggers can include a variety of viral infections, certain drugs, immobility, dehydration, stress, surgery, some oral contraceptive pills and pregnancy.


Are people affected differently by APS?

Yes. Some people are affected by symptoms more than others, while others may have the antiphospholipid antibodies (aPL) but do not develop any blood clots and/or have pregnancy complications.

The symptoms can range from low grade to potentially fatal, and people are definitely affected in different ways – for some people, APS is not debilitating, while for others, it can be a disabling condition.

As of yet, we don’t know the reason why these anomalies exist because so much research still needs to be carried out.


How is APS diagnosed?

APS is diagnosed from a combination of positive blood tests and symptoms. If you are displaying symptoms, you need to book an appointment with your GP and ask to be tested for antiphospholipid antibodies (aPL).

There are three different tests used to diagnose APS, and they are all looking for antiphospholipid antibodies (aPL):

• Anticardiolipin antibodies (aCL)
• Lupus anticoagulant (LA)
• Anti-beta2-glycoprotein-1 (anti-B2GP1)

The reason for the three tests is that they measure aPL in different ways, which means that one test alone could miss the diagnosis. The LA is a very confusing name and is not a test for lupus.

If any of the tests are positive, it will be necessary to repeat them because harmless aPL can be detected in the blood for brief periods in association with a wide variety of infections such as chickenpox and certain drugs, including antibiotics and some blood pressure tablets. For this reason, the tests should be repeated after 6-12 weeks.


Do anticoagulants such as aspirin, heparin, rivaroxaban or warfarin affect the test results?

Aspirin does not affect any of the test results, and neither does rivaroxaban, but warfarin does interfere with the results of the confusingly named Lupus Anticoagulant test.

It is possible to switch from warfarin to heparin, but it can take approximately ten days, and heparin can occasionally affect the interpretation too. Therefore, it is important that you discuss this with a specialist before you proceed.


Can the antiphospholipid antibodies (aPL) fluctuate?

Yes, as with other autoimmune disorders, aPL antibody levels can vary at times; the cause of this is unknown. Although the aPL can elevate and fall, sometimes to be so low as to be virtually undetectable, this is usually the case once you have a diagnosis of APS.


Can you catch APS?

No – it is not infectious.


Is APS hereditary?

As it is becoming more widely believed that there is a genetic tendency for the immune system to become overactive and create antiphospholipid antibodies (aPL), this means there is a greater probability that some people will inherit something from their parents that predisposes them to develop APS.

Anecdotally, there is a tendency for the condition to run in a number of families, usually from female to female or male to male, but not always. Also, affected family members often have other autoimmune conditions, such as rheumatoid arthritis, lupus or thyroid disease.

It is hoped that a large research study into this question will occur in the future.


How common is APS?

This is difficult to gauge as the condition is often under-recognised and undiagnosed, and few large-scale epidemiological studies have been conducted to provide prevalence data.

However, evidence from a robust study carried out in 2019: "The Epidemiology of Antiphospholipid Syndrome. A Population‐Based Study" indicates that the prevalence of APS in the population is 1 in every 2000, which means it can be classified as a rare disease.

APS can affect all age groups, from infancy to old age, but the majority of patients are aged between 20 and 50 years old. It is more common among women – for every two men with APS, seven women are affected.


Is there a cure for APS?

As of yet, there is no cure for APS, and the current treatment aims to prevent clotting by ‘thinning’ the blood with anticoagulants. However, there is research underway which is looking at suppressing or removing the antibodies.


What is the outlook for patients?

The outlook for many patients is positive, particularly those who have been diagnosed early and treated appropriately.

Despite being a potentially life-threatening condition, the general prognosis for most APS patients is good. With the correct treatment and lifestyle changes, the majority of patients can lead a relatively normal life, provided they continue with their medication.

However, unfortunately, a small number of people with APS continue to experience blood clots despite extensive treatment – the reasons for this are still unknown.


What type of doctor do I need to visit?

The type of specialist you will need to see will depend on your symptoms (such as a neurologist who deals with the central nervous system or an obstetrician if you are pregnant) but, usually, the type of doctor who specialises in APS is either a haematologist or rheumatologist.


What is INR?

INR is an acronym for International Normalised Ratio, which relates to the rate at which your blood clots. People taking warfarin have their INR regularly tested to ensure it is in the range specified by their doctor.

The INR test was developed so that tests would be standard throughout the world, allowing people who have to take life-long warfarin to travel and get comparable blood tests wherever they are.

It is only relevant if you are being treated with warfarin; if you take other anticoagulants such as aspirin, clopidogrel, heparin and rivaroxaban, you will not need to measure your INR.


If I have APS, does this mean I will develop lupus?

No. Approximately 35% of people with lupus will have antiphospholipid antibodies, although not all will develop APS. The same does not apply to people with primary APS, and research so far has shown that very few patients go on to develop lupus.


What causes it?

Currently, we simply don’t know why people develop APS – learn about our current understanding of the possible causes and triggers.

Find Out More »

What is it?

The antiphospholipid syndrome (APS) is an autoimmune disease which affects the blood and its ability to clot.

Find Out More »

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