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Stavros Apostolakis, MD, PhD; Renee M. Sullivan, MD; Brian Olshansky, MD; Gregory Y. H. Lip, MD
Author and Funding Information

From the University of Birmingham Centre for Cardiovascular Sciences (Drs Apostolakis and Lip), City Hospital; University of Missouri Health Care (Dr Sullivan); and the Division of Cardiovascular Medicine, University of Iowa Hospitals and Clinics (Dr Olshansky).

Correspondence to: Gregory Y. H. Lip, MD, University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Dudley Rd, Birmingham, B18 7QH, England; e-mail: g.y.h.lip@bham.ac.uk


Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Lip has served as a consultant for Bayer; Astellas Pharma; Merck & Co; Sanofi; Bristol-Myers Squibb/Pfizer Inc; Daiichi Sankyo, Inc; BIOTRONIK; Portola Pharmaceuticals, Inc; and Boehringer-Ingelheim GmbH and has been on the speakers’ bureau of Bayer, Bristol-Myers Squibb/Pfizer Inc, Boehringer-Ingelheim GmbH, and Sanofi-Aventis. Drs Apostolakis, Sullivan, and Olshansky have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2014;145(1):188-189. doi:10.1378/chest.13-2641
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To the Editor:

The letter by Dr Skov and colleagues is a small external validation of the SAMeTT2R2 (sex female, age < 60 y, medical history [more than 2 comorbidities], treatment [interacting drugs, eg, amiodarone for rhythm control], tobacco use [doubled], race [doubled]) score1 to predict international normalized ratio control in a cohort of 182 patients with excellent quality anticoagulation (time in therapeutic range [TTR] = 76%). The mean TTR of their patients with SAMeTT2R2 score ≥ 2 was the same as those with a SAMeTT2R2 score of 0 to 1.

Although we value the authors’ input, we have to underscore some important limitations of their study. First, SAMeTT2R2 was not developed to “predict” TTR, as the authors suggest, but was developed to identify anticoagulation control “outliers” within an anticoagulated population. In our cohort, the SAMeTT2R2 score performed optimally in identifying patients with average TTRs below the fifth or the 10th percentile of the center’s average. We would encourage the authors to measure the predictive performance of the SAMeTT2R2 score in identifying patients with TTR less than the fifth or the 10th percentile of their center’s average, notwithstanding their small sample size.

Also, the study by Dr Skov and colleagues may be profoundly underpowered to detect differences in TTR among subpopulations. This is reflected by some “controversial” observations—for instance, they suggest that female sex is associated with numerically better TTR. Similar to our study, the Veterans Affairs Study to Improve Anticoagulation (VARIA) investigators concluded in a much larger cohort that female sex, minority status, and multiple comorbidities negatively affected TTR.2

Our other studies (unpublished data) in substantially larger populations (N > 1,000) show usefulness of the SAMeTT2R2 score even in cohorts with overall median TTR of 73%, as well as the relation of a high SAMeTT2R2 score (> 2) to thromboembolism and bleeding (reflecting likely poor TTR3).

In conclusion, the SAMeTT2R2 was derived from a cohort with a “realistic” anticoagulation control. The average TTR was approximately 0.65, but there was also a wide range of TTR, with 10% of the population having TTR < 0.40, which is typical of the real world practice. In such populations, the SAMeTT2R2 score will be a valuable tool to guide treatment. We fully agree with the authors’ conclusion that in exceptionally “super-efficient” centers with average TTR of 75%, the use of SAMeTT2R2 score to help decision-making is probably less likely to be required.

References

Apostolakis S, Sullivan RM, Olshansky B, Lip GYH. Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: the SAMe-TT2R2Score. Chest. 2013;144(5):1555-1563. [CrossRef] [PubMed]
 
Rose AJ, Hylek EM, Ozonoff A, Ash AS, Reisman JI, Berlowitz DR. Patient characteristics associated with oral anticoagulation control: results of the Veterans AffaiRs Study to Improve Anticoagulation (VARIA). J Thromb Haemost. 2010;8(10):2182-2191. [CrossRef] [PubMed]
 
Gallego P, Roldan V, Marín F, et al. Cessation of oral anticoagulation in relation to mortality and the risk of thrombotic events in patients with atrial fibrillation [published online ahead of print October 7, 2013]. Thromb Haemost. doi:10.1160/TH13-07-0556.
 

Figures

Tables

References

Apostolakis S, Sullivan RM, Olshansky B, Lip GYH. Factors affecting quality of anticoagulation control among patients with atrial fibrillation on warfarin: the SAMe-TT2R2Score. Chest. 2013;144(5):1555-1563. [CrossRef] [PubMed]
 
Rose AJ, Hylek EM, Ozonoff A, Ash AS, Reisman JI, Berlowitz DR. Patient characteristics associated with oral anticoagulation control: results of the Veterans AffaiRs Study to Improve Anticoagulation (VARIA). J Thromb Haemost. 2010;8(10):2182-2191. [CrossRef] [PubMed]
 
Gallego P, Roldan V, Marín F, et al. Cessation of oral anticoagulation in relation to mortality and the risk of thrombotic events in patients with atrial fibrillation [published online ahead of print October 7, 2013]. Thromb Haemost. doi:10.1160/TH13-07-0556.
 
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