Effects of HCQ on AnxA5 anticoagulant activity of plasmas from APS patients. HCQ (1 mg/mL) significantly improved the AnxA5 anticoagulant activities of APS plasmas that were exposed to the same concentration (30 μg/mL) of AnxA5 (183 ± 45% vs 156 ± 33% without HCQ; P < .001). This assay, described in “Effects of HCQ on AnxA5 anticoagulant activity,” and previously,¹⁴  is a coagulation assay that measures the effect of test plasma on the binding of AnxA5 to phospholipids present in a prothrombin time-activated partial thromboplastin time reagent.