title: The Influence of Assay Selection on Prothrombin Time Measured in Patients Treated With Rivaroxaban for Nonvalvular Atrial Fibrillation.
abstract: BACKGROUND
  Prothrombin time (PT) can provide a qualitative assessment of the relative intensity of anticoagulation by rivaroxaban. More than ten types of assay are available for the measurement of PT in clinical settings, but it is not yet fully understood whether their interactions with rivaroxaban are uniform or inconsistent.
  
  
  METHODS
  We examined 139 blood samples from patients taking rivaroxaban. We measured PT using five different commercially available assays. We also evaluated the estimated rivaroxaban concentration using a chromogenic anti-factor Xa assay.
  
  
  RESULTS
  The median estimated concentration of rivaroxaban was 192 ng/ml (interquartile range 85-284 ng/ml). The correlation coefficient (r) between PT and the estimated concentrations of rivaroxaban was as follows: Thromborel S, r = 0.768; Thrombocheck PT, r = 0.861; Coagpia PT-N, r = 0.909; Neoplastin Plus, r = 0.882; and Triniclot PT Excel S, r = 0.870. The gradients of the regression plots differed more than fourfold, and the standard deviation of the regression line ranged from 1.001 to 2.980, which tended to be higher for the assays with the higher regression slope gradients.
  
  
  CONCLUSIONS
  The estimated concentration of rivaroxaban varied greatly depending on the assay, so the PT measured in patients taking rivaroxaban should be interpreted with caution.
authors.affiliation: Department of Laboratory Medicine, Tenri Hospital, Tenri, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Shimomura
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan. nakagawa@tenriyorozu.jp.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nakagawa
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kondo
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tamura
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Amano
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Enomoto
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Naoaki
authors.initials: N
authors.lastname: Onishi
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Yodo
authors.initials: Y
authors.lastname: Tamaki
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Miyake
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kaitani
authors.affiliation: Department of Cardiology, Tenri Hospital, Tenri, Japan.
authors.forename: Chisato
authors.initials: C
authors.lastname: Izumi
authors.affiliation: Department of Laboratory Medicine, Tenri Hospital, Tenri, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Fukuda
authors.affiliation: Department of Laboratory Medicine, Tenri Hospital, Tenri, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Nakamura
authors.affiliation: Division of Laboratory Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Kawano
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000097:blood / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011516:Prothrombin / Q000378:metabolism*; D012189:Retrospective Studies; D000069552:Rivaroxaban / Q000097:blood / Q000627:therapeutic use*; D018709:Statistics, Nonparametric; D013997:Time Factors
chemical_list: D000925:Anticoagulants; D011516:Prothrombin; D000069552:Rivaroxaban
keywords: anticoagulants; atrial fibrillation; monitoring; prothrombin time; rivaroxaban