Patients recruitment
This was a single-center, prospective cohort study conducted at Peking Union Medical College Hospital (PUMCH) from May 2017 to January 2020. A total of 312 consecutive patients were included in this study, of which 100 patients had been diagnosed with primary APS (PAPS group), 51 with APS secondary to SLE (SAPS group), 71 with SLE (SLE group), and 90 health controls (HC group). Diagnosis of APS was defined by clinicians according to the 2006 Sydney revised classification criteria. Sera samples were collected and immediately profiled of aPL antibodies at the Key Laboratory of Department of Rheumatology, Peking Union Medical College Hospital (PUMCH). Besides aPL serology, clinical manifestations were recorded for PAPS, SAPS, and SLE groups, including thrombosis (arterial or venous), pregnancy morbidity, microangiography (deep venous thrombosis, pulmonary embolism, etc.), and history of adverse pregnancy. For HC group, only aPL serology information was present. The study was approved by ethics committee at PUMCH and fulfilled the ethical guidelines of the declaration of Helsinki. All subjects gave written informed consent.