The definitive diagnosis of antiphospholipid syndrome requires the fulfillment of at least 1 clinical criterion and 1 laboratory criterion. There are three main laboratory criteria: lupus anticoagulant, anticardiolipin antibody, and anti-beta2 glycoprotein I antibody. 1. The presence of lupus anticoagulant in plasma, tested according to international guidelines, with a minimum of 2 positives, each separated by a period of at least 12 weeks. 2. Standard ELISA detects high/moderate titer IgM/IgG type anti-cardiolipin antibodies in plasma or serum, with at least 2 results at intervals greater than or equal to 12 weeks. 3. Standard ELISA detects IgM/IgG-type anti-beta2 glycoprotein 1 antibody in plasma or serum with at least 2 results at intervals of 12 weeks and more. The diagnosis of antiphospholipid syndrome is confirmed when one of the above experimental criteria is present, along with clinical criteria.