24th July 2024

Antiphospholipid syndrome

APLS is an autoimmune condition that presents with both venous and arterial thrombosis as well as obstetric complications such as first trimester miscarriage.

The exact mechanism of thrombus generation in APLS is not known, however it is thought that the presence of antiphospholipid antibodies along with minor vascular injuries or increased inflammation predispose the body to vascular events.

Investigations in APLS

General screening is not recommended. Testing should be aimed at those with a high probability of having APLS, such as patients with clots in unusual locations, unprovoked VTE in under 50s and obstetric complications associated with autoimmune disease.

Diagnosis is made using clinical and serological features:

• Clinical features suggestive of APLS include arterial and venous clots and complications in pregnancy, such as recurrent miscarriage or intrauterine growth restriction
• There must be positive serology in the form of lupus anticoagulant, anti-cardiolipin antibodies or anti-beta2 glycoprotein. The antibodies must be present on at least two occasions, 12 weeks apart. Antiphospholipid antibodies alone do not satisfy the criteria for APLS diagnosis

Management of APLS

Often, anticoagulation is given indefinitely.

In non-pregnant patients, LMWH followed by long-term use of warfarin is the standard treatment. INR targets vary. In those with confirmed APLS and a first venous thrombosis, INR target should be 2-3. However, if there is an arterial thrombosis, the INR target should be >3 or 2-3 with aspirin.

Pregnant women should be treated with LMWH only.

Risk factor modification is vital and patients should be encouraged to modify traditional cardiovascular risk factors such as obesity, smoking and hyperlipidaemia.