Antiphospholipid syndrome (APS) is an autoimmune disorder characterized by thrombosis and pregnancy morbidity in patients with persistently positive antiphospholipid antibodies (aPLs). However, large-scale research on general population with persistent aPLs has been lacking. This project proposes to establish the first multicenter cohort of patients with persistently positive aPLs in China and conduct a comprehensive clinical phenotyping study. Based on traditional phenotypes of thrombotic and pregnancy events, the focus will be on extra-standard clinical phenotypes and prospective assessment of event risk and prognosis in aPL-positive population. A prospective analysis of extra-standard antibodies will also be conducted to recommend detection criteria for extra-standard antibody application in China and to assess their clinical significance.

Chinese AntiphosPholipid Syndrome cohorT cOllaborative NEtworks (CAPSTONE) is a national research network created to register patients with persistent aPLs. We aim at enrolling 2000 patients from a total of six centers, lead by the Peking Union Medical College Hospital (PUMCH). The aPLs assay will be validated in the central lab in PUMCH. All patients will be followed every six months, and up to three years. Thrombotic and pregnancy events related to aPLs will be recorded, as well as extra-criteria clinical phenotypes.

Inclusion Criteria:

• The presence of one or more of the antiphospholipid antibodies (aPL) tested according to the 2006 Sapporo APS clasification criteria, on two or more occasions at least 12 weeks apart:

Exclusion Criteria:

• Patients refuse to participate;
• Unable to be followed.

All patients with the presense of one or more of the following aPLs can be included, after obtaining the written informed consent. The aPLs include: 1)IgG and/or IgM anticardiolipin antibodies (aCL) in moderate or high titer (>40 GPL or MPL units, respectively, or a titer >99th percentile for the testing laboratory), measured by a standardized enzyme-linked immunosorbent assay (ELISA). 2) IgG and/or IgM anti-beta2-glycoprotein (GP) I >40 GPL or MPL units, respectively, or a titer >99th percentile for the testing laboratory, measured by a standardized ELISA according to recommended procedures. 3) Lupus anticoagulant (LA) activity detected according to published guidelines.