Antiphospholipid syndrome diagnostic criteria

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Feham Tariq, MD [2]


The diagnosis of antiphospholipid syndrome is made in cases of a clinical event (vascular thrombosis or pregnancy event) and repeated positive tests of aPL performed 12 weeks apart (repeat aPL testing is necessary due to the naturally occurring presence of transient low levels of aPL following infections).

Diagnostic Criteria for Antiphospholipid syndrome

The Updated Sapporo APS Classification Criteria are commonly used for APS diagnosis.[1] Based on these criteria, APS diagnosis requires:

  • a) Vascular Thrombosis (blood clots) in any organ or tissue or Pregnancy Event (one or more miscarriages after 10th week of gestation, three or more miscarriages before 10th week of gestation, or one or more premature births before 34th week of gestation due to eclampsia) and
  • b) Persistenly (12 weeks apart) Positive aPL (lupus anticoagulant test, moderate-to-high titer anticardiolipin antibodies, or moderate-to-high titer β2-glycoprotein-I antibodies).

The International Consensus Statement is commonly used for Catastrophic APS diagnosis.[2] Based on this statement, Definite CAPS diagnosis requires:

  • a) Vascular Thrombosis in three or more organs or tissues and
  • b) Development of manifestations simultaneously or in less than a week 'and
  • c) Evidence of small vessel thrombosis in at least one organ or tissue and
  • d) Laboratory confirmation of the presence of aPL.

Some serological tests for syphilis may be positive in aPL-positive patients (aPL bind to the lipids in the test and make it come out positive) although the more specific tests for syphilis that use recombinant antigens will be negative.

Diagnostic criteria for catatrophic antiphospholipid syndrome (CAPS)

  • Diagnostic criteria for CAPS is as follows:
Classification criteria for CAPS
1. Evidence of involvement of three or more organs, systems, and/or tissues
2. Development of manifestations simultaneously or in less than a week
3. Confirmation by histopathology of small vessel occlusion in at least one organ or tissue
4. Laboratory confirmation of the presence of antiphospholipid antibodies (lupus anticoagulant, anticardiolipin antibodies, and/or anti-beta2-glycoprotein I antibodies)
Definite CAPS
  • Requires all four criteria
Probable CAPS
  • All four criteria, except for only two organs, systems, and/or sites of tissue involvement or
  • All four criteria, except for the laboratory confirmation at least six weeks apart due to the early death of a patient never tested for aPL before the catastrophic APS or
  • Criteria 1, 2, and 4 above or
  • 1, 3, and 4 and the development of a third event in more than a week but less than a month, despite anticoagulation


  1. Miyakis S, Lockshin MD, Atsumi T, Branch DW, Brey RL, et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost 2006;4:295-306)
  2. Asherson RA, Cervera R, de Groot PG; et al. (2003). "Catastrophic antiphospholipid syndrome: international consensus statement on classification criteria and treatment guidelines". Lupus. 12 (7): 530–4. PMID 12892393.

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