Development of a pharmacogenetic-based warfarin dosing algorithm and its performance in Brazilian patients: highlighting the importance of population-specific calibration.

Background: The main aims of the present study were to develop a pharmacogenetic-based warfarin dosing algorithm and to validate it in a highly admixed population.

Materials & Methods: We included two patient cohorts treated with warfarin (first cohort, n = 832; and second cohort, n = 133).

Results: Our algorithm achieved a determination coefficient of 40% including the variables age, gender, weight, height, self-declared race, amiodarone use, enzyme inducers use, VKORC1 genotypes and predicted phenotypes according to CYP2C9 polymorphisms.

Conclusion: Data suggest that our developed algorithm is more accurate than the IWPC algorithm when the application is focused on patients from the Brazilian population. Population-specific derivation and/or calibration of warfarin dosing algorithms may lead to improved performance compared with general use dosing algorithms currently available. Original submitted 26 November 2014; Revision submitted 9 April 2015.