Key result
Plasma warfarin levels predict changes in serial prothrombin times, explaining ~15% of total variance.
Why the study?
The relative contribution of changes in plasma warfarin levels to variation in serial steady-state prothrombin times was not well defined.
Do changes in plasma warfarin levels predict variations in steady-state prothrombin times in patients on long-term oral anticoagulation?
Population
129 otherwise healthy patients requiring long-term oral anticoagulation with warfarin
Comparison
Serial prothrombin times and paired plasma total warfarin levels
Design
Prospective observational cohort study at two outpatient anticoagulation clinics
Authors
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Warfarin levels may aid prothrombin time interpretation during long-term anticoagulation; leaves open the contribution of pharmacodynamic variability or measurement error.
Cohort (n=129)
Yes
Do changes in plasma warfarin levels predict variations in steady-state prothrombin times in patients on long-term oral anticoagulation?
Effect estimate: R2 = 0.75
p-value: p=0.0001
Plasma warfarin levels strongly predict changes in serial prothrombin times, though individual sensitivity varies widely, suggesting pharmacodynamic changes or measurement errors play a major role.
White et al. (1995) conducted a cohort in Long-term oral anticoagulation therapy (n=129). Plasma warfarin levels was evaluated on Variation in serial steady-state prothrombin times (R2 = 0.75, p=0.0001). Plasma warfarin levels significantly predicted changes in serial steady-state prothrombin times (R2 = 0.75, p = 0.0001), with 15.3% of total variance attributable to the effect of warfarin.
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