Why it is so important to be in the therapeutic range

How well an INR is managed is represented by the time spent in the therapeutic range. In medical language this is called TTR (Time in Therapeutic Range).

In other words: If my INR-values remain within the set therapeutic range for all or almost all of the time, the chances for bleeding or thromboembolism decrease. Prof. Alan Jacobson, (Loma Linda, California) clearly said, "Yes" to the importance of "TTR" at the 7th International Conference of ISMAAP in Lyon, France (4th to 5th November 2011). His opinion is that a “TTR” of 80 to 90% is achievable for a group of highly motivated patients. However, in many countries the time spent within the therapeutic range is not higher than 70 – 75%. The so-called "TTR" is also mentioned in studies, e.g. whether or not  a new drug is better in comparison to Vitamin-K-antagonists. So far, INR self-testing patients have not been included in such studies. Worldwide, there are approx. 300,000 patients performing INR self-management, with over half of these patients being in Germany.

A.M. Gallagher (Thrombosis and Haemostasis 106.5/2011) assesses the relationship between the TTR and the risk of strokes and mortality in a study group of 37,907 Warfarin patients with atrial fibrillation in the UK. It was shown that on average only 63% of patients were within the therapeutic range. The comparison of the two groups of patients, which, on average were 30% and 70% within the therapeutic range, respectively showed a decrease in strokes of 79%.

In the same edition, G. Y. H. Lip asks, whether strokes can be better prevented by taking Warfarin (similar to Phenprocoumon). Referring to the work of Gallagher, he emphasizes that a well-managed treatment with anticoagulants protects patients with atrial fibrillation sufficiently from stroke.

Patients who test their coagulation values themselves belong to the group of highly motivated patients. Taking the treatment with anticoagulants into their own hands and therefore (acting independently) or taking responsibility themselves is one of the significant components for an optimal INR control and a high "TTR".

Christian Schaefer (Feb., 2012)