To examine the prevalence of multiple antiphospholipid antibodies (aPL) subtypes in healthy people and antiphospholipid syndrome (APS) patients, and to assess the value of IgA-aPL in the diagnosis of APS. According to the 2006 Sydney International APS Classification Criteria, a total of 218 APS patients who were admitted to Peking Union Medical College Hospital or West China Hospital of Sichuan University from July to December 2019 were enrolled. Among them, 66 were males, and 152 were females, aged (44.5±15.4) years, including 148 primary APS patients and 70 secondary APS patients. Age-and gender-matched controls were collected at the same period at the ratio of 1∶1 with the APS cases. IgA/IgG/IgM anticardiolipin antibodies (aCL) and anti-β glycoprotein I antibodies (aβGPI) were detected by chemiluminescent immunoassay. The differences of indicators between groups were analyzed, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of IgA-aPL for APS. The positivity of IgA-aCL and IgA-aβGPI was 20.6% and 15.6% in the APS patients, while in the IgG/IgM-aCL or IgG/IgM-aβGPI negative individuals, the isolated positivity of IgA-aCL and IgA-aβGPI was only 2.3% and 0.9%, respectively. Accordingly, IgA-aCL and IgA-aβGPI isolated positivity could be used to diagnose APS (=0.216, 1, respectively). The area under the ROC curve (AUC) of IgG/IgM-aCL for APS diagnosis was 0.833, which was significantly better than that of IgG-aCL alone (AUC=0.776, 0.05). Besides, patients with IgA-aPL were more likely to have heart valve lesions and thrombocytopenia (both <0.05). Based on the existing serological markers, such as lupus anticoagulant, IgG/IgM subtype of aCL and aβGPI, testing IgA-aCL and IgA-aβGPI cannot further improve the predictive value of APS. However, IgA-aPL is associated with clinical manifestations of APS, including heart valve lesions and thrombocytopenia.

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