Antiphospholipid syndrome

What is Antiphospholipid syndrome?

Antiphospholipid syndrome (APS) is a clinical and laboratory entity consisting of persistent antibodies directed against phospholipid (aPL) in conjunction with recurrent venous or arterial thrombosis and obstetric signs.

Table I: Clinical and laboratory criteria for APS

Clinical criteria
(One or more criteria)

Laboratory criteria
(One or more criteria,
present on at least 2 occasions 12 weeks apart)

one or more confirmed arterial, venous or small-vessel thromboses in any part of the body

Circulating lupus anticoagulant, measured by International Society on Thrombosis and Haemostasis (ISTH) criteria

Obstetric signs:

  • one or more unexplained deaths of a morphologically normal foetus at or beyond the 10th week of gestation, or
  • one or more premature births of a morphologically normal neonate before the 34th week of gestation because of eclampsia, pre-eclampsia or placental insufficiency, or
  • 3 or more spontaneous abortions before the 10th week of gestation

Anticardiolipin antibodies (IgG or IgM), in moderate or high titre (> 40 GPL or MPL, or > 99th percentile), measured by a standardised ELISA

Anti-ß2-glycoprotein-I antibodies (IgG or IgM), present in titre > 99th percentile, measured by a standardised ELISA

APS can occur even in the absence of any autoimmune disease, in which case it is referred to as primary APS.
Where it arises in a patient presenting an autoimmune disease, the term "secondary APS" is used.

If an autoimmune disease is diagnosed in a patient with primary APS, the latter is subsequently referred to as secondary APS.