Warfarin Genotyping Reduces Hospitalization Rates. Results From the MM-WES (Medco-Mayo Warfarin Effectiveness Study)

Robert S. Epstein, Thomas P. Moyer, Ronald E. Aubert, Dennis J. OKane, Fang Xia, Robert R. Verbrugge, Brian F. Gage, J. Russell Teagarden

Research output: Contribution to journalArticlepeer-review

294 Scopus citations


Objectives: This study was designed to determine whether genotype testing for patients initiating warfarin treatment will reduce the incidence of hospitalizations, including those due to bleeding or thromboembolism. Background: Genotypic variations in CYP2C9 and VKORC1 have been shown to predict warfarin dosing, but no large-scale studies have prospectively evaluated the clinical effectiveness of genotyping in naturalistic settings across the U.S. Methods: This national, prospective, comparative effectiveness study compared the 6-month incidence of hospitalization in patients receiving warfarin genotyping (n = 896) versus a matched historical control group (n = 2,688). To evaluate for temporal changes in the outcomes of warfarin treatment, a secondary analysis compared outcomes for 2 external control groups drawn from the same 2 time periods. Results: Compared with the historical control group, the genotyped cohort had 31% fewer hospitalizations overall (adjusted hazard ratio [HR]: 0.69, 95% confidence interval [CI]: 0.58 to 0.82, p < 0.001) and 28% fewer hospitalizations for bleeding or thromboembolism (HR: 0.72, 95% CI: 0.53 to 0.97, p = 0.029) during the 6-month follow-up period. Findings from a per-protocol analysis were even stronger: 33% lower risk of all-cause hospitalization (HR: 0.67, 95% CI: 0.55 to 0.81, p < 0.001) and 43% lower risk of hospitalization for bleeding or thromboembolism (HR: 0.57, 95% CI: 0.39 to 0.83, p = 0.003) in patients who were genotyped. During the same period, there was no difference in outcomes between the 2 external control groups. Conclusions: Warfarin genotyping reduced the risk of hospitalization in outpatients initiating warfarin. (The Clinical and Economic Impact of Pharmacogenomic Testing of Warfarin Therapy in Typical Community Practice Settings [MHSMayoWarf1]; NCT00830570).

Original languageEnglish
Pages (from-to)2804-2812
Number of pages9
JournalJournal of the American College of Cardiology
Issue number25
StatePublished - Jun 22 2010


  • comparative effectiveness
  • genotyping
  • pharmacogenomics
  • warfarin

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