Table 1.

Preliminary criteria for the classification of catastrophic APS

1) Evidence of involvement of three or more organs, systems and/or tissuesa 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 tissueb 4) Laboratory confirmation of the presence of antiphospholipid antibodies (lupus anticoagulant and/or anticardiolipin antibodies)c

Definite catastrophic APS All four criteria Probable catastrophic APS All four criteria, except for only two organs, systems and/or tissues involvement All four criteria, except for the absence of laboratory confirmation at least six weeks apart due to the early death of a patient never tested for aPL before the catastrophic APS 1, 2 and 4 1, 3 and 4 and the development of a third event in more than a week but less than a month, despite anticoagulation

^aUsually, clinical evidence of vessel occlusions, confirmed by imaging techniques when appropriate. Renal involvement is defined by a 50% rise in serum creatinine, severe systemic hypertension (> 180/100mmHg) and/or proteinuria (> 500mg/24hours).

^bFor histopathological confirmation, significant evidence of thrombosis must be present, although vasculitis may coexist occasionally.

^cIf the patient had not been previously diagnosed as having an APS, the laboratory confirmation requires that presence of antiphospholipid antibodies must be detected on two or more occasions at least six weeks apart (not necessarily at the time of the event), according to the proposed preliminary criteria for the classification of definite APS.⁹