To investigate the clinical characteristics in patients with primary antiphospholipid syndrome (PAPS) and to identify potential predictors of thrombotic events.

A total of 107 patients with PAPS were enrolled in our study, who were admitted in Peking Union Medical College Hospital from January 2004 to December 2014. Demographic data, age at onset, disease duration, past history of hypertension and regular cigarette smoking, clinical manifestations, imaging characteristics, management and prognosis were retrospectively collected. Bivariate statistical analysis and logistical regression test were performed to compare the discrepancy between patients with or without thromboembolic events.

In 107 patients, there were 65 female and 42 male patients, with mean age (39.8±15.8) years old, median disease duration 10.5 (2.0, 48.0) months. A total of 72(67.3%) patients reported episodes of thromboembolic events, including 72 venous thromboses and 29 arterial thromboses. The most frequent venous thromboses were deep vein thromboses (35.5%), pulmonary embolism the second common (29.9%), with cranial venous sinus thromboses the following (8.4%). In arterial thromboembolic events, the incidence of transient ischemic attack (TIA) and ischemic stoke was the highest(14.0%), embolism of lower extremities the second (6.5%), and 4 patients (3.7%) with acute myocardial infarction. Sixty seven patients(62.6%)had positive lupus anticoagulant, 60 patients(56.1%)with positive anticardiolipin antibody, 32 patients(29.9%, 32/74) with positive β ₂ glycoprotein Ⅰ(β₂GPⅠ). Forty patients(37.4%)had double positive antibodies, while 19 cases(17.8%)with triple positive. In logistical regression, aging (per 10 years) and hypocomplementemia were significantly related to venous thrombosis (OR=1.421, 95%CI 1.066-1.894, P<0.05, andOR=6.435, 95%CI 1.374-30.130, P<0.05, respectively). Cigarette smoking and triple positive antibodies were independent risk factors of arterial thrombosis (OR=3.996, 95%CI 1.079-14.795, P<0.05 andOR=3.166, 95%CI 1.102-9.097, P<0.05, respectively).

APS is an autoimmune disorder characterized by recurrent arterial and venous thromboembolic events. Venous thromboembolism is more common than the arterial. Age and hypocomplementemia are predictors of venous thromboembolism; while smoking and triple positive antibodies are independent risk factors of arterial thromboembolism.

Antiphospholipid syndrome; Thrombosis; Antiphospholipid antibodies; Hypocomplementemia; Anticoagulation