The SAMe-TT 2 R 2 score and quality of anticoagulation in atrial fibrillation : a simple aid to decision-making on who is suitable ( or not ) for vitamin K antagonists

Maintaining the therapeutic range in patients treated with vitamin K antagonists (VKAs) had always been challenging whilst the potential consequences of deviating from the optimal average time in therapeutic range(TTR) are deleterious in patients with atrial fibrillation (AF), given the risk for thromboembolic and bleeding events. Variousclinical decision-making toolshavebeen developed tohelp decision-making in the management of AF patients. In 2013, a new score—with the acronym SAMe-TT2R2—was proposed to help identify those patients who were likely to have a propensity to poor INR control (as reflected by average time in the therapeutic range [TTR] ,65%). This simple score based on clinical features may help identify those AF patients who would do well on VKA (SAMe-TT2R2 score 1⁄4 0–2), or conversely, those who might require additional interventions to achieve acceptable anticoagulation control (SAMe-TT2R2 score .2). 3 This score was derived from a trial cohort and thus independent validation in ‘real-world’ AF cohorts would be needed. In the current issue of EP-Europace, Abumaileq et al. performed a retrospective analysis of a cohort of outpatients with non-valvular AF and found that SAMe-TT2R2 could indeed represented a useful clinical tool to identify a poor quality of anticoagulation control with VKAs. The predictive ability of SAMe-TT2R2 was acceptable for identifying low TTR and improved when integrated with other clinical characteristics. A strong relationship between quality of anticoagulation and clinical outcomeshaspreviouslybeendemonstrated, thus supporting its use as a relevant outcome variable. At least three different methods are identified for quantifying quality of anticoagulation. All three metrics have known advantages and disadvantages and may be utilized for clinical management or research. Time in the therapeutic range, or percent of days in the therapeutic range, has been defined with a methodology described by Rosendaal, but it is not as simple to calculate as it might seem. It is calculated by incorporating the frequency of INR measurements and their actual values, and assuming that changes between consecutive international normalized ratio (INR) measurements are linear over time. This calculation looks at the amount of time between visits to determine how long the patient might have been within the therapeutic range. If an INR (the therapeutic range 2.0–3.0), tested in 1 January is 2.5, then 3.5 when tested in 31 January, one may think that the patient slowly moved from 2.5 to 3.5 over those 30 days. It is assumed that 15 days were in the therapeutic range, and 15 days were out of the range within the 30-day time period, which means the patient was within the range 50% of the time. Assessment of TTR with such linear interpolation is the only method that incorporates time. The calculation is obviously becoming more complex and will often need a computer as soon as the results are not as archetypal as in our example and when tests are not performed on a perfectly regular basis. The per cent of visits in the range looks at how many visits had INR results in the therapeutic range, and divides by the total number of visits. If the patient has had nine visits, and six had INR readings within the therapeutic range, then the patient is considered to be in the range 66% of the time. This method was used in the study by Abumaileq et al. The authors defined it as the percentage of INRs in therapeutic range (PINRR). The two methods of assessment— TTR and PINNR—are different and not absolutely interchangeable. The evaluation of quality of anticoagulation with PINNR is not the