Time in therapeutic range

Synonyms and Keywords: TTR

Overview
Time in therapeutic range estimates the time a patient remains in the narrow therapeutic range of an international normalized ratio (INR) of 2-3. Going above this range increase your bleeding risk while going below steeply increases the risk of stroke.

Factors Affecting Time in Therapeutic Range (TTR)
Cross trial comparisons of TTR are hampered by variations in:

CHADS Score
A higher CHADS score is associated with a lower TTR. Sicker patients may have reduced access to frequent testing.

Congestive Heart Failure (CHF)
The presence of congestive heart failure Varying drug clearance and distribution (CHF: 63% in ROCKET, 32% RELY, 35% ARISTOTLE)

Country
The TTR is highest in Scandanavian countries (70% to 80%), and lowest in developing countries (40% to 50%)

Comparison of results across trials in TTR are inappropriate unless the TTR in each country should be compared, ROCKET AF in those countries who conducted RE-LY and vice versa (adjusting for the number of sites in each country).