title: Clinical Validation of R-T Estimation for CoaguChek XS INR Results.
abstract: Despite the emergence of several new oral anticoagulants, warfarin remains a widely used form of anticoagulation that continues to have a role in the treatment of cardiac and thrombotic conditions.
  
  
  
  The goal of this study was to evaluate whether the R-T estimation, an equation developed in a previous study, was a valid clinical tool in managing patients' warfarin therapy in an anticoagulation clinic in lieu of obtaining a venipuncture international normalized ratio (INR) secondary to a high CoaguChek XS (CXS) INR.
  
  
  
  This study used a randomized double-blind method to compare the clinical decisions made using venipuncture or CXS machine and recorded the INR, percentage dose change, time to clinical decision from check-in, and scheduled follow-up.
  
  
  
  In the analysis of the difference in percentage dose change, a 1.0% (95% CI = -0.78 to 2.68; P = 0.27) difference was observed overall, and a 1.2% (95% CI = -0.59 to 2.95; P = 0.18) difference was observed in the 4 to 5.9 subgroup. Clinical decisions were reached 17 minutes faster (95% CI = 11-24; P < 0.001) overall and 17 minutes faster (95% CI = 10-24; P < 0.001) in the 4 to 5.9 subgroup. Scheduled follow-up was 0.38 weeks sooner (95% CI = 0.01-0.67; P = 0.014) overall and 0.36 weeks sooner (95% CI = 0-0.66; P = 0.041) in the 4 to 5.9 subgroup.
  
  
  
  The results of this study support the use of the R-T estimation for correction of INR values obtained using the CXS meter when the INR is in the range of 4 to 5.9. This correction will allow clinics using this device to more efficiently manage patients taking warfarin.
authors.affiliation: UF Health Shands Hospital, Gainesville, FL, USA richtc@shands.ufl.edu.
authors.forename: Christopher
authors.initials: C
authors.lastname: Richter
authors.affiliation: University of Florida College of Pharmacy, Gainesville, FL, USA.
authors.forename: James
authors.initials: J
authors.lastname: Taylor
authors.affiliation: UF Health Shands Hospital, Gainesville, FL, USA.
authors.forename: Joyanna
authors.initials: J
authors.lastname: Wright
authors.affiliation: University of Florida Department of Medicine, Gainesville, FL, USA.
authors.forename: Bradley
authors.initials: B
authors.lastname: Fletcher
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D001071:Appointments and Schedules; D001777:Blood Coagulation / Q000187:drug effects*; D003657:Decision Making; D004311:Double-Blind Method; D016903:Drug Monitoring / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D005260:Female; D005431:Florida; D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D018962:Phlebotomy; D019095:Point-of-Care Systems / Q000592:standards; D015203:Reproducibility of Results; D013997:Time Factors; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: INR; ambulatory care; anticoagulation; point-of-care; warfarin