Monitoring anticoagulation in patients with an unreliable prothrombin time/international normalized ratio: factor II versus chromogenic factor X testing. Blood Coagul Fibrinolysis 2014 Apr;25(3):232-6
Date
04/01/2014Pubmed ID
24681704Pubmed Central ID
PMC4350672DOI
10.1097/MBC.0000000000000030Scopus ID
2-s2.0-84897474955 (requires institutional sign-in at Scopus site) 15 CitationsAbstract
The international normalized ratio (INR) can be unreliable in patients with lupus anticoagulants (LACs) or other conditions affecting baseline testing. Alternative methods to assess anticoagulation on warfarin through measures of vitamin K-dependent factor activity by clot based or chromogenic assays may be necessary. In this patient population, the ideal method is unknown. Thirty-six patients stable on warfarin with LAC or unreliable INR testing had an INR, a prothrombin time-based clotting assay for factor II (FII) activity, and a chromogenic assay for factor X (CFX) activity were performed simultaneously. Eighty-nine sets of measurements were obtained of which 83 sets included all three assays. CFX and FII levels were well correlated (r = 0.92) in all patients and in 26 patients with a documented antiphospholipid antibody (r = 0.93). Parallel testing was seen in 99% of FII assays. Sixty-one percent of CFX and 57% of FII were within the therapeutic range. In 32 CFX and FII pairs wherein assessment of anticoagulation was discordant, 16 CFX agreed with INR and 13 FII agreed with INR (McNemar's, χ = 0.14, P = 0.7). The number of times tests were discrepant was not statistically different between CFX and FII (P = 0.36). CFX and FII activity are well correlated in patients that require alternative monitoring of warfarin. Either test can be used in this population.
Author List
Baumann Kreuziger LM, Datta YH, Johnson AD, Zantek ND, Shanley R, Reding MTAuthor
Lisa M. Baumann Kreuziger MD Associate Professor in the Medicine department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnticoagulantsBlood Coagulation
Blood Coagulation Tests
Drug Monitoring
Factor X
Female
Humans
International Normalized Ratio
Male
Middle Aged
Prothrombin
Prothrombin Time
Warfarin
