Table 3.

Clinical and laboratory criteria established for the research of definite APS

Clinical criteria 1. Vascular thrombosis One or more clinical episodes of an arterial, venous or small vessel thrombosis, confirmed by imaging or Doppler studies or histopathology, without significant evidence of inflammation in the vessel wall 2. Obstetric morbidity  a. One (or more) unexplained demise of a morphologically normal fetus at or beyond 10 weeks of gestation, or  b. One or more premature births of a morphologically normal neonate at or before 34 weeks of gestation, due to severe preeclampsia or severe placental insufficiency, or  c. At least 3 unexplained consecutive miscarriages <10 weeks of gestation; known factors associated with recurrent miscarriage including parental genetic, anatomical and endocrinological factors should be ruled out

Laboratory criteria 1. ACL IgG and/or IgM in blood, present in medium or high titres (>40 GPL or MPL or >99th percentile) on 2 or more occasions at least 12 weeks apart, measured by standardized ELISA 2. Anti-β2-glycoprotein I antibody of the IgG and/or IgM isotype in blood (>99th percentile) on 2 or more occasions at least 12 weeks apart, measured by ELISA 3. Lupus anticoagulant present in plasma on 2 or more occasions at least 12 weeks apart, detected according to the Guidelines of the International Society on Thrombosis and Haemostasis, which include the following steps  a. Prolonged phospholipid-dependent coagulation using a screening test such as the activated partial thromboplastin time, kaolin clotting time, dilute Russell's viper venom time, dilute prothrombin time  b. Failure to correct the prolonged coagulation time on the screening tests by mixing with normal plasma  c. Shortening or correction of the prolonged coagulation time on the screening tests by the addition of excess phospholipids or platelets  d. Exclusion of other coagulopathies (e.g., factor VIII inhibitor) or heparin

At least 1 clinical and 1 laboratory criterion must be present for definite APS. From Miyakis et al. [110].