Genotype-Guided Warfarin Dosing Reduces Adverse Events After Hip, Knee Arthroplasty

By Amy Orciari Herman

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

Genotype-guided dosing of warfarin in older adults undergoing elective hip or knee arthroplasty helps prevent adverse events, according to a JAMA study.

Roughly 1600 adults aged 65 and older were randomized to either genotype-guided or clinically guided warfarin for 11 days, beginning the night before or the night of arthroplasty. In both groups, clinical variables were used to guide dosing; in the genotype group, dosing also took into account four polymorphisms associated with warfarin metabolism, warfarin sensitivity, and vitamin K metabolism.

The primary outcome — a composite of major bleeding, INR of 4 or greater, or death within 30 days, and venous thromboembolism within 60 days — occurred in 11% of the genotype-guided group versus 15% of the clinically guided group. The benefit was largely due to fewer cases of elevated INR with genotype-guided treatment.

An editorialist concludes, "Genotype-guided warfarin dosing probably has some clinical utility but it might be simpler and less expensive to implement wider use of clinical dosing algorithms to reduce the harms of anticoagulation."