Premium
Use of the Chromogenic Factor X Assay to Predict the International Normalized Ratio in Patients Transitioning from Argatroban to Warfarin
Author(s) -
Arpino Paul A.,
Demirjian Zareh,
Cott Elizabeth M.
Publication year - 2005
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1592/phco.25.2.157.56950
Subject(s) - argatroban , chromogenic , medicine , coagulation , warfarin , area under the curve , gastroenterology , chromatography , chemistry , thrombin , platelet , atrial fibrillation
Study Objective. To determine the clinical utility of the chromogenic factor X level for conversion from argatroban to warfarin in hospitalized patients. Design. Prospective observational study. Patients. Sixty‐two hospitalized patients with indications for anticoagulation in whom the chromogenic factor X assay was used for conversion from argatroban to warfarin. Setting. University‐affiliated hospital. Intervention. From December 2003–May 2004, data for all patients in whom the chromogenic factor X assay was used for conversion from argatroban to warfarin were screened for inclusion. When the chromogenic factor X level was satisfactory, the clinician discontinued the argatroban and a confirmatory international normalized ratio (INR) was obtained. Measurements and Main Results. To determine the ability of the chromogenic factor X level to predict the INR free of argatroban influence, we calculated the sensitivity and specificity by using a cutoff chromogenic factor X level of 45% or less, or greater than 45%, which corresponded to an INR of 2 or greater, or less than 2, respectively. We constructed a receiver operating characteristic curve to illustrate various cutoff levels of chromogenic factor X. Of 146 patients screened, 62 had data that met criteria for analysis. An average of 6 ± 3 doses of warfarin were administered before the confirmatory coagulation studies were obtained. The average time from the chromogenic factor X measurement to obtainment of confirmatory coagulation studies was 9 ± 4 hours. Use of a chromogenic factor X level of 45% or less to predict an INR of 2 or greater absent of argatroban influence had a sensitivity of 93%, a specificity of 78%, and an accuracy of 89%. The area under the receiver operating characteristic curve was 0.91 (95% confidence interval 0.81–0.99, p<0.0001). Conclusion. The chromogenic factor X level is an accurate alternative when converting hospitalized patients from argatroban to warfarin. A chromogenic factor X level of 45% or less is a reliable predictor that the INR will be therapeutic when argatroban therapy is discontinued.