Time in therapeutic range (TTR) is important for the effectiveness and safety of warfarin. TTR has been found to be poor in recent studies which in part explains the favorable profile of target specific oral anticoagulants in comparison to warfarin.
It was hoped early on that genomic testing to guide dosing would have a favorable impact on TTR and hence clinical effectiveness. But when subjected to the scrutiny of clinical investigation the field has been controversial if not disappointing.
Two recent studies recently published in NEJM   have conflicting results and hence will do little to resolve the controversy. TTR as a whole in these studies was poor.