Relationship between chromogenic factor X and international normalized ratio differs during early warfarin initiation compared with chronic warfarin administration

Rosborough, Terry K.; Jacobsen, Jennifer M; Shepherd, Michele F.

doi:10.1097/mbc.0b013e32832ca31f

Cited by 6 publications

(4 citation statements)

References 6 publications

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“…The best fit model of the relationship between CFX and INR was inverse with a natural log transformation of both variables. Modeling a quadratic relationship with reciprocal transformation of INR, as has been reported in previous studies [16] showed increased sensitivity to outliers in our data. This may be because we had fewer data points at the extreme INR values and our patients were on stable warfarin dosing.…”

Section: Discussionsupporting

confidence: 67%

Monitoring anticoagulation in patients with an unreliable prothrombin time/international normalized ratio

Kreuziger

Datta

Johnson

et al. 2014

Blood Coagulation &Amp; Fibrinolysis

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The International Normalized Ratio (INR) can be unreliable in patients with lupus anticoagulants (LAC) 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. Methods 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 performed simultaneously. Results 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 where assessment of anticoagulation was discordant, 16 CFX agreed with INR and 13 FII agreed with INR (McNemar’s, χ2=0.14, p=0.7). The number of times tests were discrepant was not statistically different between CFX and FII (p=0.36). Conclusions Chromogenic factor X and factor II activity are well correlated in patients that require alternative monitoring of warfarin. Either test can be used in this population.

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Section: Discussionsupporting

confidence: 67%

Monitoring anticoagulation in patients with an unreliable prothrombin time/international normalized ratio

Kreuziger

Datta

Johnson

et al. 2014

Blood Coagulation &Amp; Fibrinolysis

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“…A higher variability with recombinant thromboplastin reagents has been demonstrated in non-APS patients in the initial phase of VKA therapy as well as those with unstable INR values [23][24][25]. This has been primarily attributed to variations in the concentration of factor VII due to its short plasma half-life (t H ≈6 h).…”

Section: Inr Differences Between Different Pt Assaysmentioning

confidence: 95%

Monitoring anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome

et al. 2015

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Because of the possible interference of antiphospholipid antibodies (APL) with the phospholipid component of thromboplastin reagents, concerns have been raised about the validity of international normalized ratio (INR) testing to monitor anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome (APS). To investigate the reliability of the INR, we determined the INR using various prothrombin time (PT) assays and compared the results with those of a chromogenic factor X (CFX) assay. The study cohort consisted of 40 APS patients and 100 APL-negative patients who were on anticoagulant therapy for reasons other than APS. The agreement (i.e. the percentage of patients with a difference ≤0.5 INR units) between the PT-derived INR and CFX-derived INR equivalents was only moderate in both patient groups. The best agreement with CFX-derived INR equivalents was observed for the Thromborel S reagent in APS patients (69.1 %) and for Neoplastin Plus in APL-negative patients (72.0 %). Regarding the results for the point-of-care system CoaguChek XS, an agreement between the INR and the CFX-derived INR equivalent was less frequently observed in the APS patients (55.6 vs. 67.8 %; p = 0.050). When considering all 3058 pairs of INR tests within the international sensitivity index (ISI)-calibrated range of 1.5 to 4.5 s, we did not observe a higher variability of INR values in either the APS patient group or the subgroup of APS patients positive for lupus coagulants compared with the APL-negative controls. In conclusion, monitoring vitamin K antagonists (VKA) therapy with laboratory INR measurements seems to be suitable for the majority of APS patients.

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“…The supratherapeutic INR category of greater than 3.0 correlated with a mean CFX of 20.8% (range, 9% to 46%) (n=104). In 2009, Rosborough et al 27 identified that the relationship between CFX and INR varies among patients with initiation of warfarin vs those receiving long-term warfarin therapy. They reported a 7% to 18% higher level of CFX activity for a given INR value during warfarin initiation compared with patients receiving long-term warfarin therapy and suggested predictive formulas for each phase of therapy.…”

Section: Discussionmentioning

confidence: 99%

Chromogenic Factor X Assay for Monitoring Warfarin Anticoagulation in a Child With a Prosthetic Mitral Valve

Greenmyer

Niaz

Kohorst

et al. 2021

Mayo Clinic Proceedings: Innovations, Quality & Outcomes

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Mechanical mitral valve replacement in infants and young children is associated with substantial morbidity and mortality. Lifelong anticoagulation is required, with all the accompanying challenges of maintaining levels in infants and children whose dietary input continually changes. Even with careful control of all aspects that can perturb the coagulation cascade, these patients have a substantial lifelong risk of thrombotic and hemorrhagic complications that can also affect the durability of the valve. Anticoagulation is usually achieved utilizing warfarin with the degree of anticoagulation measured via the international normalized ratio (INR). Unfortunately, in some cases, the INR can be falsely elevated and lead to inappropriate reassurance. We describe a 4-year-old patient with complex congenital heart disease palliated via a single ventricular pathway with a mechanical atrioventricular valve replacement. The patient experienced acute valvular thrombosis while receiving warfarin with INR at target levels. Chromogenic factor X (CFX) levels were discordant with INR measurements, suggesting a subtherapeutic level of anticoagulation despite maintaining the standard INR target. Therefore, CFX levels were used to interpret INR measurements and guide an individualized approach to anticoagulation. We propose a new role of CFX: to verify and guide warfarin anticoagulation in high-risk pediatric patients including those undergoing mechanical mitral valve replacement.

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Relationship between chromogenic factor X and international normalized ratio differs during early warfarin initiation compared with chronic warfarin administration

Cited by 6 publications

References 6 publications

Monitoring anticoagulation in patients with an unreliable prothrombin time/international normalized ratio

Monitoring anticoagulation in patients with an unreliable prothrombin time/international normalized ratio

Monitoring anticoagulant therapy with vitamin K antagonists in patients with antiphospholipid syndrome

Chromogenic Factor X Assay for Monitoring Warfarin Anticoagulation in a Child With a Prosthetic Mitral Valve

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