Influence of dietary vitamin K intake on subtherapeutic oral anticoagulant therapy.

It is unclear what advice should be given to patients using vitamin K antagonists with respect to dietary vitamin K intake. We performed a nested case-control study in patients attending a Dutch anticoagulation clinic, to determine the association between vitamin K intake and subtherapeutic International Normalized Ratio (INR) values and the interaction between usual and recent vitamin K intake. Compared to patients with a normal usual vitamin K intake, those with a high vitamin K intake had a decreased risk of a subtherapeutic INR [Hazard Ratio (HR) 0.

Subtherapeutic oral anticoagulant therapy: frequency and risk factors.

Subtherapeutic anticoagulation levels increase both the risk and severity of thromboembolism. The aim of this study was to determine the cumulative incidence of subtherapeutic international normalised ratios (INRs) and to identify risk factors associated with a low INR. We performed a cohort study in 7,419 patients from a Dutch anticoagulation clinic.