Feasibility study of the Fearon Algorithm in anticoagulation service guided warfarin management

Background

Patients receiving warfarin who spend a lower proportion of time in therapeutic international normalized ratio (INR) range (TTR) have a higher risk of both bleeding complications and thromboembolic events. Using warfarin dosing algorithms is one intervention associated with improved INR stability.

Objective

To determine the feasibility of an individualized warfarin dosing algorithm (Fearon Algorithm) under anticoagulation management service (AMS) care and compare measures of INR control using the algorithm with standard care.

Methods

A pre/post intervention feasibility study consisting of the 12 months prior to patient enrollment (pre-study phase) and 6 months in which patients used the Fearon Algorithm under the supervision of an AMS pharmacist (AMS phase). The primary study outcome was the change in individual TTR.

Results

A total of 30 patients were enrolled in the study, 26 (87%) of whom successfully completed the AMS study phase using the Fearon Algorithm. Median corrected individual TTR increased significantly from 53% (IQR: 39%, 64%) during the year prior to enrollment to 63% (IQR: 57%, 73%) during the AMS phase (p < 0.01) The uncorrected TTR also increased significantly from 52% (IQR: 39%, 64%) to 61% (IQR: 57%, 72%) (p < 0.01). The Fearon Algorithm specified a smaller warfarin tablet strength in half the patients.

Conclusion

The Fearon Algorithm is feasible for an AMS to implement in patients receiving long-term warfarin therapy and appears to improve TTR.