Antiphospholipid syndrome (also known as APS, sticky blood syndrome, or Hughes Syndrome) is an acquired thrombophilic disorder in which autoantibodies are produced to a variety of phospholipids and phospholipid binding proteins.1,2
APS can be caused by antibodies to lupus anticoagulant, cardiolipin, or β2-glycoprotein I. This means that patients are at increased risk of thrombotic events.1
The most common vascular manifestations of APS are deep venous thrombosis of lower limbs, pulmonary embolism, and cerebral ischemic attack; early and late miscarriages are the major features of obstetric APS. In the catastrophic variant of APS, multiple small-vessel thrombotic events occur at different sites.3 Female patients appear to more frequently demonstrate the clinical features of arthritis, livedo reticularis, and migraine; whereas male patients more often develop myocardial infarction, epilepsy, and lower extremity arterial thrombosis.1
One of the main risk factors for APS is the presence of other autoimmune conditions. For example,
A clinical syndrome resembling multiple sclerosis has also been described in APS, raising the issue of a correct differential diagnosis.1,3
Patients who should be screened for antiphospholipid antibodies include:4
Patients with unprovoked proximal deep vein thrombosis or pulmonary embolism after stopping anticoagulation for at least seven days
Young adults, (i.e. aged under 50), with ischemic stroke
Women with recurrent pregnancy loss, defined as more than 3 pregnancy losses before 10 weeks gestation
Patients should be tested for lupus anticoagulant, IgG anti-cardiolipin, and IgG anti-β2-glycoprotein I.2,4 Due to the low sensitivity of these tests they should always be interpreted in the context of each other and the clinical history. Lupus anticoagulant is the most predictive test for thrombosis. The presence of IgG anti-cardiolipin or IgG anti-β2-glycoprotein I, in those who are lupus anticoagulant positive, increases specificity. There is nothing to suggest that measuring IgM antibodies in patients with thrombosis adds useful information. Tests should be repeated after an interval of 12 weeks to demonstrate persistence.4
Clinical and laboratory assessments are very important to provide a full picture of APS, helping clinicians to tailor care depending on the patient's risk profile1,2
The risk of thrombosis in patients with APS is estimated to range from 0.5-30%1
Recurrent miscarriage occurs in about 1% of the general population attempting to have children, with about 10-15% of these women being diagnosed with APS3
APS is more common in women than men in about a 5:1 ratio. The mean age of onset of the clinical manifestations of APS is 31 years, although APS may be seen in children and older patients as well1
What are the benefits of early diagnosis?
Detailed clinical and laboratory assessments are very important to provide a full picture of APS. Using lupus anticoagulant, IgG anti-cardiolipin, and IgG anti-β2-glycoprotein I can help:2
Confirm a diagnosis of APS
Identify patients at higher risk of recurrence or developing clinical events
Provide patients with appropriate treatment (dependant on their risk profile) earlier in their journey, potentially improving their quality of life
How can tests be used to personalise care?
Using lupus anticoagulant, IgG anti-cardiolipin, and IgG anti-β2-glycoprotein I, APS patients should be divided into four categories:2
Category I includes patients with more than one positive test in any combination
Category IIA describes patients who are lupus anticoagulant-positive
Category IIB describes patients who are anti-cardiolipin-positive
Category IIC describes patients who are anti-β2 glycoprotein I-positive
Patients carrying both anti-cardiolipin and anti-β2 glycoprotein I isotypes are at higher risk of developing clinical events.2
Triple positivity is the most predictive profile for clinical manifestations and recurrences despite conventional treatment.2
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