So far, only the RE LY trial has reported event rates with warfarin as they relate to individuals' (not center) INR time in range.  The comparison of events by center TTR may be misleading because even good "centers" with TTRs close to 70% may have a majority of patients with individual TTRs < 60%; and the patients with TTRs < 60% appear to have 2 to 3 times the event rate as those with TTRs > 70%.

In RE LY 50% of warfarin treated patients had an individual TTR > 67%.  Among this group, the composite endpoing of stroke, SEE, MI, PE, major bleed and death was about 5.3%/yr vs 7.09%/yr with dabi 100 mg and 6.91%/yr with dabi 150 mg.  That calculates to an NNT to prevent one major event of about 15.2 with warfarin @ INR > 67% vs NNT of 21 for dabi 100 mg and 20 for dabi 150 mg.  Therefore, it would appear that fairly well managed warfarin is superior to either dose of dabi. with a relative risk reduction of about 24% and an absolute risk reduction of about 1.7%.  This would all be academic if achieving a TTR > 67% was cumbersome, costly, and difficult.  Four small recent trials have reported on improved INR control with INR self-testing and online management.  The mean TTRs achieved were 71.4%, 80.4%, 65.9% (not so good), and 79.7%.  Two of the trials recorded clinician management time as < 10 min/patient/4 "visits" per month and in one trial the patients reported an average of 10 min per "visit" to perform self testing and complete an online interaction.  If maintaining a patient's TTR @ > 70% can be achieved easily with little time, hassle, and expense, then well-managed VKA therapy may be a superior.  

Ref: Bussey HI. J Thromb and Thrombolysis 2011; 31:265-274. 

Conflicts:  Unpaid consultant in the development of ClotFree, one of the software systems used in one of the 4 studies mentioned above and recipient of the Chest Foundations GSK Distinguished Scholar in Thrombosis for a proposal to develop and test an online management system for INR self-testing patients.