Criteria for the Classification of the Antiphospholipid Syndrome (APS)

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Clinical Criteria

Vascular thrombosis

  • One or more clinical episodes of arterial, venous, or small-vessel thrombosis, occurring within any tissue or organ

Complications of pregnancy

  • One or more unexplained deaths of morphologically normal fetuses at or after the 10th week of gestation; or
  • One or more premature births of morphologically normal neonates at or before the 34th week of gestation; or
  • Three or more unexplained consecutive spontaneous abortions before the 10th week of gestation

Laboratory Criteria

Anticardiolipin antibodies

  • Anticardiolipin IgG or IgM antibodies present at moderate or high levels in the blood on two or more occasions at least six weeks apart

Lupus anticoagulant antibodies

  • Lupus anticoagulant antibodies detected in the blood on two or more occasions at least six weeks apart, according to the guidelines of the International Society on Thrombosis and Hemostasis

A diagnosis of definite antiphospholipid syndrome requires the presence of at least one of the clinical criteria and at least one of the laboratory criteria. No limits are placed on the interval between the clinical event and the positive laboratory findings.

The following antiphospholipid antibodies are currently not included in the laboratory criteria: anticardiolipin IgA antibodies, anti-B2-glycoprotein I antibodies, and antiphospholipid antibodies directed against phospholipids other than cardiolipin (e.g., phosphatidylserine and phosphatidylethanolamine) or against phospholipid-binding proteins other than cardiolipin-bound B2-glycoprotein I (e.g., prothrombin, annexin V, protein C, or protein S).




  1. Levine JS, Branch DW, Rauch J. The antiphospholipid syndrome. N Engl J Med. 2002 Mar 7;346(10):752-63. [Medline]
  2. Greaves M, Cohen H, MacHin SJ, Mackie I. Guidelines on the investigation and management of the antiphospholipid syndrome. Br J Haematol. 2000 Jun;109(4):704-15.[Medline]
  3. Alving BM. Diagnosis and management of patients with the antiphospholipid syndrome. J Thromb Thrombolysis. 2001 Sep;12(1):89-93.[Medline]


Created: Mar 24, 2006