Poor correlation of supratherapeutic international normalised ratio and vitamin K-dependent procoagulant factor levels during warfarin therapy.
Patients with a supratherapeutic international normalised ratio (ST-INR) are at risk for bleeding. ST-INR is corrected by withholding warfarin therapy and often by supplementing vitamin K or providing vitamin K-dependent factors; the exact therapeutic decision is based on the extent of the prolonged INR. Currently, ST-INRs are frequently observed in clinical practice due to the use of sensitive recombinant tissue thromboplastin reagents and automation. However, there are scant data correlating an ST-INR with various vitamin K-dependent factors. This prospective cohort study, set in a large tertiary care teaching hospital for the University of Texas Southwestern Medical Center at Dallas, defined the relationship between ST-INR (>5.0) and measured vitamin K-dependent procoagulant factors. Prothrombin time, INR and vitamin K-dependent factors II, VII, IX and X were measured in 78 patients with an INR > 5.0 (ST-INR) who were on warfarin therapy for more than 2 months. There was no significant relationship between the ST-INR and levels of important vitamin K-dependent factors II and X. These data support the recent guidelines that the management of an INR > 5.0 should be driven by the clinical determinants rather than specific INR values per se.
Sarode
Ravindra
R
Department of Pathology, The University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9073, USA. ravi.sarode@utsouthwestern.edu
Rawal
Ajay
A
Lee
Ray
R
Shen
Yu-Min
YM
Frenkel
Eugene P
EP
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000097:blood / Q000188:drug therapy; D001778:Blood Coagulation Disorders / Q000097:blood / Q000188:drug therapy*; D001779:Blood Coagulation Factors / Q000032:analysis*; D005170:Factor X / Q000032:analysis; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011516:Prothrombin / Q000032:analysis; D012044:Regression Analysis; D020521:Stroke / Q000097:blood / Q000188:drug therapy; D020246:Venous Thrombosis / Q000097:blood / Q000188:drug therapy; D014812:Vitamin K / Q000627:therapeutic use*; D014859:Warfarin / Q000627:therapeutic use*
D000925:Anticoagulants; D001779:Blood Coagulation Factors; D014812:Vitamin K; D014859:Warfarin; D011516:Prothrombin; D005170:Factor X