Key result
In patients on oral anticoagulants, the within-subject total variation of INR was 10.1%, requiring a critical difference of 0.7 at a 2.5 target and 1.0 at a 3.5 target for significant change.
Why the study?
What is the critical difference in serial INR measurements required to indicate a statistically significant biological change necessitating dose adjustment in patients on oral anticoagulants?
Population
32 patients receiving oral anticoagulant therapy at pharmacological steady-state
Design
Cohort
Follow-up
6 months
Authors
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Requires caution interpreting small INR fluctuations before dose adjustment; leaves open prospective validation of these thresholds.
Cohort (n=32)
What is the critical difference in serial INR measurements required to indicate a statistically significant biological change necessitating dose adjustment in patients on oral anticoagulants?
A change in INR of at least 0.7 (at target 2.5) or 1.0 (at target 3.5) is required to represent a true biological change rather than analytical/biological variation, guiding dose adjustments in oral anticoagulant therapy.
Lassen et al. (1995) conducted a cohort in Patients receiving oral anticoagulant therapy (n=32). Serial measurements of prothrombin time (INR) was evaluated on Within-subject total variation of prothrombin time (INR) and critical difference. In patients on oral anticoagulants, the within-subject total variation of INR was 10.1%, requiring a critical difference of 0.7 at a 2.5 target and 1.0 at a 3.5 target for significant change.
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