Use of the chromogenic factor X assay in patients transitioning from argatroban to warfarin therapy

Pharmacotherapy. 2012 Jun;32(6):493-501. doi: 10.1002/j.1875-9114.2012.01050.x. Epub 2012 Apr 17.

Abstract

Study 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.

Design: Retrospective medical record review.

Setting: Academic medical center and community-based teaching hospital.

Patients: 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.

Measurements and main 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.

Conclusion: 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.

MeSH terms

  • Academic Medical Centers
  • Anticoagulants / administration & dosage*
  • Anticoagulants / adverse effects
  • Anticoagulants / therapeutic use
  • Arginine / analogs & derivatives
  • Blood Coagulation / drug effects*
  • Chromogenic Compounds
  • Databases, Factual
  • Drug Administration Schedule
  • Electronic Health Records
  • Factor X / analysis*
  • Hospitals, Teaching
  • Humans
  • International Normalized Ratio*
  • Male
  • Middle Aged
  • Pipecolic Acids / administration & dosage*
  • Pipecolic Acids / adverse effects
  • Pipecolic Acids / therapeutic use
  • Predictive Value of Tests
  • Retrospective Studies
  • Sensitivity and Specificity
  • Sulfonamides
  • Warfarin / administration & dosage*
  • Warfarin / adverse effects
  • Warfarin / therapeutic use

Substances

  • Anticoagulants
  • Chromogenic Compounds
  • Pipecolic Acids
  • Sulfonamides
  • Warfarin
  • Factor X
  • Arginine
  • argatroban