title: Use of the chromogenic factor X assay in patients transitioning from argatroban to warfarin therapy.
abstract: OBJECTIVE
  To assess the correlation between the chromogenic factor X assay and the international normalized ratio (INR) in patients transitioning from argatroban to warfarin therapy.
  
  
  METHODS
  Retrospective medical record review.
  
  
  METHODS
  Academic medical center and community-based teaching hospital.
  
  
  METHODS
  One hundred thirty-nine patients who had chromogenic factor X levels measured during the transition from argatroban to warfarin therapy between January 1, 2006, and July 31, 2010.
  
  
  RESULTS
  The correlation between chromogenic factor X levels and INRs during the transition period was assessed by calculating the sensitivity, specificity, positive predictive value, and negative predictive value for chromogenic factor X levels that were less than or equal to 45% in predicting a therapeutic INR (2.0-3.5). Patients received an average of 4.4 doses of warfarin before argatroban was discontinued. In 60 patients (43.2%), chromogenic factor X levels were subtherapeutic at the time of argatroban discontinuation. Chromogenic factor X levels could predict a therapeutic INR with a sensitivity of 63.2%, a specificity of 80%, a positive predictive value of 93.5, and a negative predictive value of 32.3. In patients who received 5 or more days of warfarin overlap with argatroban, the sensitivity of chromogenic factor X levels to predict an INR greater than 2.0 was 78.2%, with a specificity of 77.8%, a positive predictive value of 95.6, and a negative predictive value of 36.8. The correlation of chromogenic factor X levels and a therapeutic INR was 18.1%; however, this poor correlation may have been due to increases in the INR values of the patients who received less than 5 days of warfarin overlap with argatroban. During the transition period, nine patients developed thrombi and eight patients experienced clinically significant bleeding.
  
  
  CONCLUSIONS
  Measuring chromogenic factor X levels is recommended before transitioning patients from argatroban to warfarin therapy. Patients should receive at least 5 days of overlap with warfarin and have a chromogenic factor X level of 45% or less before discontinuing argatroban.
authors.affiliation: Department of Pharmaceutical Services, Emory University Hospital, 1364 Clifton Road NE, Atlanta, GA 30322, USA.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Austin
authors.forename: Candace R
authors.initials: CR
authors.lastname: Stearns
authors.forename: Anne M
authors.initials: AM
authors.lastname: Winkler
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Paciullo
mesh_terms: D000046:Academic Medical Centers; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D001120:Arginine / Q000031:analogs & derivatives; D001777:Blood Coagulation / Q000187:drug effects*; D002863:Chromogenic Compounds; D016208:Databases, Factual; D004334:Drug Administration Schedule; D057286:Electronic Health Records; D005170:Factor X / Q000032:analysis*; D006784:Hospitals, Teaching; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010875:Pipecolic Acids / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013449:Sulfonamides; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D002863:Chromogenic Compounds; D010875:Pipecolic Acids; D013449:Sulfonamides; D014859:Warfarin; D005170:Factor X; D001120:Arginine; C031942:argatroban