Antiphospholipid Syndrome (APS) is an autoimmune disorder of blood clotting and pregnancy loss. It is associated with proteins called antiphospholipid antibodies (aPL) in the blood. Blood clotting in this disease occurs for several reasons; one reason involves the interaction of aPL with another protein found on the surface of the cells that line blood vessels (endothelial cells). This protein, called annexin A5 (AnxA5), forms a shield over the surface of these cells. The AnxA5 Resistance Assay is a blood test that can detect when there is a problem with the protective AnxA5 shield on endothelial cell surfaces.~This 12 week study will observe patients with persistent aPL in the blood who are starting a medicine called hydroxychloroquine (HCQ). The primary goal of the study is to compare results of the AnxA5 resistance assay from patients before they start taking HCQ and after they have taken it for 12 weeks to see if the results of the blood test change. Our secondary goal is to measure a variety of other blood tests before and after patients have started taking HCQ; these tests include D-dimer, Activated Protein C (APC) Resistance, and aPL titers/status (LA test, aCL ELISA, aß2GPI ELISA, and anti-Domain-I ß2GPI ELISA).
This 12 week study will observe patients with and without systemic lupus erythematosus who have persistent antiphospholipid antibodies in the blood who are starting a medicine called hydroxychloroquine. It will measure if these patients have a change in a blood test called the annexin A5 resistance assay over that 12 week period.