Table 1.

Summary of Inclusion and Exclusion criteria.

Inclusion criteria	Exclusion criteria
Elective hip or knee arthroplasty (not hip fracture)	Currently taking warfarin
≥65 years of age	Incarcerated or institutionalized
Has Medicare Part B	Thrombocytopenia (platelets < 75K)
Warfarin prophylaxis anticipated for at least 4 weeks	History of venous thromboembolism
Reliable telephone access	History of thrombophilia
Willing to give consent (English only)	History of major bleeding or bleeding disorder (e.g. hemophilia, von Willebrand disease, etc.)
Willing/able to have Doppler Ultrasound at 4–6 week follow-up visit	Planned administration of any anticoagulant other than warfarin (except heparin flushes)
Baseline INR <1.35	Warfarin genotypes or prior therapeutic warfarin dose known
Life expectancy >6 months	Warfarin allergy
	Unlikely to be compliant (e.g. history of non-compliance, substance abuse, etc.)
	First degree relative with VTE before age 50
	Planned administration of interacting medications, except those taken into account by WarfarinDosing.org*
	Alcoholism not in remission for past 6 months

^*carbamazepine, rifampin, barbiturates, phenytoin