There is currently no robust evidence for implementing a target INR range of 1.6 to 2.6, and therefore the conventional, evidence-based INR target of 2.0 to 3.0 should be employed globally. Importance of TTR INR Range: The proportion of time spent within the therapeutic INR range (INR, 2.0 to 3.0) is intrinsically linked to the risk of adverse events. The temporal pattern of INR control is most commonly calculated using the Rosendaal method of linear interpolation between 2 consecutive INR values,150 known as the TTR or by the percentage of INRs within However, a limitation of the Rosendaal method of interpolation is that INRs > 42 days apart have generally not been interpolated in studies due to large uncertainties in uctuation. Although TTR and percentage of INRs within therapeutic range are highly they are not equivalent and should not be used interchangeably. TTR is a widely accepted and validated measure of anticoagulation control and predicts adverse events in patients receiving VKA,153-155 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 Indeed, 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 Thus, when VKAs are used, attention should be focused on the average individual TTR as a measure of the quality of anticoagulation control. 