The Diagnostic Value of New Additional Antiphospholipid Antibodies in Antiphospholipid Syndrome.

Background: The antiphospholipid syndrome (APS) is an autoimmune disease that is characterized by thrombosis and/or pregnancy failure and associated with the presence of all or at least one of three standard antibodies (anti-phospholipid (aPL) antibodies, including lupus anticoagulant (LA), anti-cardiolipin (aCL), and anti-β2-glycoprotein I (anti-β2GPI)). A growing body of evidence recommends adding additional aPL antibodies, such as anti-phosphatidylserine (aPS), anti-prothrombin (aPT), and anti-annexin A5 (aAA5), to conventional laboratory tests (revised Sapporo criteria), especially in seronegative APS cases.

Objectives: We aimed to compare the diagnostic value, utility, and performance of these three additional antibodies along with the standard aPL antibodies in cases with confirmed and non-criteria APS (seronegative).

Methods: This was a prospective observational study on 59 patients who presented with clinical features of APS at the hematology, medical, rheumatology, and obstetric clinics. LA was detected by standard coagulation tests, while other aPL, IgG, and IgM antibodies (aCL, aβ2GPI, aPS, aPT, aAA5) were detected with enzyme-linked immunosorbent assay (ELISA).

Results: Anti-PS antibody was more frequent compared to aPT and aAA5 in both confirmed cases (84.6%) and non-criteria (seronegative) (15.4%) APS. As a single test, the aPS antibody was significantly better (<0.05) than the aPT and aAA5 antibodies in the detection of APS cases. Seven non-criteria patients were confirmed using additional aPL antibodies. Among these patients, four, two, and one patient was confirmed with aPS, aPT, and aAA5 antibodies, respectively.

Conclusion: Our data support the findings of previously published studies and attribute the clinical significance of additional aPL antibodies, particularly aPS, in identifying non-criteria APS cases. In the future, along with conventional aPL antibodies, these additional antibodies should be included as standard laboratory tests in the revised Sapporo criteria.