Updated International Consensus Classification Criteria for definite Antiphospholipid Antibody Syndrome

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What are the updated International Consensus Classification Criteria for definite Antiphospholipid Antibody Syndrome?

At least one of the following clinical criteria:

  • • Vascular thrombosis: one or more clinical episodes of arterial, venous, or small vessel thrombosis in any tissue or organ confirmed by imaging studies, Doppler studies or histopathology that cannot be attributed to another cause.
  • • Pregnancy morbidity occurring in a morphologically normal fetus by ultrasound or direct examination:
    • – One or more unexplained fetal deaths at >10 weeks of gestation.
    • – One or more premature births at <34 weeks of gestation due to severe preeclampsia, eclampsia, or placental insufficiency.
    • – Three or more unexplained consecutive spontaneous abortions at <10 weeks of gestation, excluding maternal anatomic or hormonal abnormalities and paternal and maternal chromosomal causes.


  • At least one of the following laboratory criteria on two or more occasions at least 12 weeks apart and not more than 5 years before the clinical manifestation:
    • • IgG and/or IgM aCL abs in moderate or high titer (>40 units of either, or >99th percentile for laboratory tests).
    • • IgG and/or IgM antibody to β2GPI at >99th percentile for laboratory tests.
    • LA activity according to following guidelines:
      • • Prolonged phospholipid-dependent coagulation test (activated partial thromboplastin time [aPTT], Kaolin clotting time, dilute Russell viper venom time [dRVVT], hexagonal phase phospholipid neutralization assay [STACLOT-LA test]).
      • • Failure to correct the prolonged coagulation time by a mix of platelet-poor normal plasma.
      • • Shortening or correction of the prolonged coagulation time with excess phospholipid.
      • • Exclusion of other coagulopathies (e.g., factor deficiencies or inhibitors, heparin, direct oral anticoagulants).

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