Since many patients who need anticoagulation will be on warfarin and may continue to be on warfarin, it is important to ask: How well are we controlling warfarin? 

Figure 14 references a recent study that used data from a very interesting database from Quest Diagnostics (West Norriton, PA).  Quest Diagnostics does a large proportion of the blood testing throughout the United States, and we were given access to this database.  We looked at the INR levels for 138,000 individuals, totaling 2.7 million INR values for the period of January 2007 through 2008, asking "How good is medical practice in the United States at maintaining therapeutic warfarin levels?”