F10 and systemic lupus erythematosus: The RVV test has been developed on the same principle as RVV time (RVVT), which is another functional test for the evaluation of anti-Xa activity; RVVT is an assay for the detection of lupus anticoagulants, but it is also affected by anti-Xa drugs, including apixaban, because RVV specifically cleaves factor X to Xa [3, 4, 15].