What is the importance of the TTR INR Range?
The temporal pattern of INR control is most commonly calculated using the Rosendaal method of linear interpolation between 2 consecutive INR values, known as the TTR or by the percentage of INRs within the therapeutic range. TTR is a widely accepted and validated measure of anticoagulation control and predicts adverse events in patients receiving VKA, and is the quality and performance measure of choice for specialized anticoagulation clinics. Numerous studies have demonstrated that the risk of thromboembolism, major bleeding, and death is lower when the proportion of TTR is higher, at least 65%. Random one off INR values give little insight into the degree of anticoagulation control, and many adverse outcomes (eg, bleeding) occur even within the therapeutic INR range of 2.0 to 3.0.