title: Activated protein C resistance in patients following venous thromboembolism receiving rivaroxaban versus vitamin K antagonists: assessment using Russell viper venom time-based assay.
abstract: : Activated protein C resistance (APC-R) is assessed as part of thrombophilia screening, preferably in patients not taking oral anticoagulants. Rivaroxaban is known to alter some APC-R assays. To our knowledge, there have been no reports on the effect of rivaroxaban on the Russell viper venom time (RVVT)-based APC-R assay in real-life patients. In 168 consecutive outpatients suspected of having venous thromboembolism because of thrombophilia, APC-R was determined using the RVVT-based ProC Ac R assay (Siemens, Marburg, Germany). Patients receiving rivaroxaban or vitamin K antagonists were eligible. We measured rivaroxaban concentrations using the anti-Xa Biophen DiXal assay (Hyphen Biomed, Neuville-Sur-Oise, France) and factor V Leiden using the real-time PCR. APC-R was detected in 23 (28%) patients on rivaroxaban (n = 81) administrated 2-48 h since the blood draw, 15 (28%) patients on vitamin K antagonists (n = 54), and in four (12%) patients off anticoagulation (n = 33). Compared with nonanticoagulated patients, APC-R ratios were similar in patients on rivaroxaban, without any correlation with rivaroxaban concentrations (from 0 to 303 μg/l). None of the patients on rivaroxaban were found to have false-negative or false-positive APC-R ratios. Rivaroxaban concentrations up to 300 μg/l do not affect results of the ProC Ac R RVVT-based assay, which could be recommended in patients referred to a clinic for thrombophilia screening in whom the time since the last dose of rivaroxaban is uncertain.
authors.affiliation: aAnalytical Laboratory, John Paul II Hospital bInstitute of Cardiology, Jagiellonian University School of Medicine, Krakow, Poland.
authors.forename: Tadeusz
authors.initials: T
authors.lastname: Goralczyk
authors.forename: Katarzyna B
authors.initials: KB
authors.lastname: Wojtowicz
authors.forename: Anetta
authors.initials: A
authors.lastname: Undas
mesh_terms: D020016:Activated Protein C Resistance / Q000209:etiology*; D000328:Adult; D065427:Factor Xa Inhibitors / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time; D000069552:Rivaroxaban / Q000008:administration & dosage*; D019851:Thrombophilia; D054556:Venous Thromboembolism / Q000150:complications* / Q000188:drug therapy; D014812:Vitamin K / Q000037:antagonists & inhibitors*
chemical_list: D065427:Factor Xa Inhibitors; D014812:Vitamin K; D000069552:Rivaroxaban