Out-of-range Results More Dangerous than Many Believe

According to a study published in the New England Journal of Medicine, the risk of adverse events grows exponentially when INR is below 2.5 or above 4.9.

In the study, researchers attempted to determine the optimal intensity by calculating the incidence of complications at different levels of anticoagulation. The intensity-specific incidence of each type of event was calculated as the number of events that occurred at a certain intensity of anticoagulation (expressed as INR divided by the number of patient-years during which the INR was at this level in the total patient population). The intensity of anticoagulant therapy for patients with prosthetic heart valves is optimal when the INR is between 2.5 and 4.9.

Source: S.C. CANNEGIETER, et all. NEJM 1995; Vol. 333 No. 1