Modified SAMe-TT₂R₂ score for predicting the therapeutic range of digoxin

Digoxin treatment has come under scrutiny in recent years after reports from several studies that it is associated with increased mortality in patients with atrial fibrillation (AF). The clinical effects of digoxin on mortality were closely related to serum digoxin concentrations (SDC) in these studies. In the present work, we evaluated the role of the SAMe-TT₂R₂ and modified SAMe-TT₂R₂ scores in predicting the therapeutic range of digoxin therapy.

Medical records from our institution were screened for patients who were under digoxin treatment between 2008 and 2018. A total of 2418 patients for whom SDC were recorded were included in the study. An SDC of <0.5 or >1.2 ng/ml was defined as being out of the therapeutic range (oTR).

In multivariable regression analyses, abnormal body mass index (odds ratio [OR]: 1.59, 95% confidence interval [CI]: 1.29-1.95, p < 0.01), white blood cell count (OR: 1.12, 95% CI: 1.01-1.27, p < 0.01), and the modified SAMe-TT₂R₂ score (OR: 4.19 95% CI: 3.71-4.72, p < 0.01) were determined to be independent predictors of oTR. A modified SAMe-TT₂R₂ score greater than 3 predicted oTR with a sensitivity of 86% and a specificity of 65% (AUC: 0.825, p < 0.01).

Digoxin is still widely used in the treatment of heart failure and AF despite concerns about the increased risk of mortality when levels are oTR. In the present study, the modified SAMe-TT₂R₂ score was found to be an independent predictor of oTR. This score may aid clinicians in identifying patients who are more likely to benefit from digoxin therapy.