Evaluation of Stable Doses of Warfarin in a Patient Cohort

Abstract

Background Definitions for stable dose of warfarin varies in the reported studies. International warfarin pharmacogenetic consortium (IWPC) algorithm was generated from the data based on these definitions. Objective In the present study, we primarily evaluated whether any significant differences exist between the definitions for stable warfarin dose. Methods A prospective cross-sectional study in adults receiving warfarin for at least 3 months was carried out. Stable doses of warfarin as defined in previous studies were compared with the standard definition. Bland-Altman plots, Pearson’s correlation and intra-class coefficients (ICC) were used to assess the correlation, reliability and agreements between the doses. Results Sixty-four patients were recruited. Twenty definitions were obtained from the previous studies. We observed that all but one showed very high or high positive correlations; and either excellent or good ICC. No significant differences between the doses initiated and predicted by IWPC algorithm. Conclusion We observed similar stable doses between the definitions except for one. Hence, IWPC algorithm may not have any bias associated with inclusion of any studies with variable definitions for stable warfarin dose.