Subscribe to RSS
Evaluation of Stable Doses of Warfarin in a Patient CohortFunding: This study was part of the research project supported by AGU RCSI 2019-2 grant.
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.
Received: 15 June 2020
Accepted: 25 July 2020
Article published online:
20 August 2020
© 2020. Thieme. All rights reserved.
Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany
- 1 Lodwick A. Warfarin therapy: A review of the literature since the Fifth American College of Chest Physicians’ consensus conference on antithrombotic therapy. Clin Appl Thromb Hemost 1999; 5: 208-215
- 2 Sridharan K, Modi T, Bendkhale S. et al. Association of genetic polymorphisms of CYP2C9 and VKORC1 with bleeding following warfarin: A case-control study. Curr Clin Pharmacol 2016; 11: 62-68
- 3 Jaffer A, Bragg L. Practical tips for warfarin dosing and monitoring. Cleve Clin J Med 2003; 70: 361-371
- 4 International Warfarin Pharmacogenetics Consortium Klein TE, Altman RB. et al. Estimation of the warfarin dose with clinical and pharmacogenetic data [published correction appears in. N Engl J Med 2009; 361: 1613
- 5 Bader LA, Elewa H. The impact of genetic and non-genetic factors on warfarin dose prediction in MENA region: A systematic review. PLoS One 2016; 11: e0168732
- 6 Kuruvilla M, Gurk-Turner C. A review of warfarin dosing and monitoring. Proc (BaylUniv Med Cent) 2001; 14: 305-306
- 7 Namazi S, Azarpira N, Hendijani F, Khorshid MB, Vessal G, Mehdipour AR. The impact of genetic polymorphisms and patient characteristics on warfarin dose requirements: A cross-sectional study in Iran. Clinical Therapeutics 2010; 32: 1050-1060
- 8 Esmerian MO, Mitri Z, Habbal MZ, Geryess E, Zaatari G, Alam S. et al. Influence of CYP2C9 and VKORC1 polymorphisms on warfarin and acenocoumarol in a sample of lebanese people. Journal of Clinical Pharmacology 2011; 51: 1418-1428
- 9 Loebstein R, Vecsler M, Kurnik D, Austerweil N, Gak E, Halkin H. et al. Common genetic variants of microsomal epoxide hydrolase affect warfarin dose requirements beyond the effect of cytochrome P450 2C9. Clinical Pharmacology and Therapeutics 2005; 77: 365-372
- 10 Wafarin dosing. Available at: http://www.warfarindosing.org/Source/InitialDose.aspx (Accessed on 20 March 2020)
- 11 Tideman PA, Tirimacco R, St John A, Roberts GW. How to manage warfarintherapy. AustPrescr 2015; 38: 44-48
- 12 Mukaka MM. Statistics corner: A guide to appropriate use of correlation coefficient in medical research. Malawi Med J 2012; 24: 69-71
- 13 Koo TK, Li MY. A Guideline of Selecting and Reporting Intraclass correlation coefficients for reliability research. J Chiropr Med 2017; 16: 346
- 14 International Warfarin Pharmacogenetics Consortium. Available at: https://www.pharmgkb.org/downloads, (Accessed on 19 Mar 2020)
- 15 An J, Niu F, Zheng C. et al. Warfarin management and outcomes in patients with non valvular atrial fibrillation within an integrated health care system. J Manag Care Spec Pharm 2017; 23: 700-712
- 16 Shoji M, Suzuki S, Otsuka T. et al. A simple formula for predicting the maintenance dose of warfarin with reference to the initial response to low dosing at an outpatient clinic. Intern Med 2020; 59: 29-35
- 17 Lazo-Langner A, Monkman K, Kovacs MJ. Predicting warfarin maintenance dose in patients with venous thromboembolism based on the response to a standardized warfarin initiation nomogram. J Thromb Haemost 2009; 7: 1276-1283
- 18 Le Gal G, Carrier M, Tierney S. et al. Prediction of the warfarin maintenance dose after completion of the 10 mg initiation nomogram: do we really need genotyping?. J Thromb Haemost 2010; 8: 90-94
- 19 Semakula JR, Mouton JP, Jorgensen A. et al. A cross-sectional evaluation of five warfarin anticoagulation services in Uganda and South Africa. PLoS One 2020; 15: e0227458
- 20 Sharabiani A, Bress A, Douzali E, Darabi H. Revisiting warfarin dosing using machine learning techniques. Comput Math Methods Med 2015; 2015: 560108
- 21 Saffian SM, Wright DF, Roberts RL, Duffull SB. Methods for predicting warfarin dose requirements. Ther Drug Monit 2015; 37: 531-538