Comparisons of CHADS₂ and CHA₂DS₂-VASc scores for stroke risk stratification in atrial fibrillation: Which scoring system should be used for Asians?

Background Both U.S. and European guidelines recommend use of the CHA₂DS₂-VASc rather than CHADS₂ score for stroke risk stratification in atrial fibrillation (AF). However, the CHA₂DS₂-VASc score has not been proved to be better than CHADS₂ score for Asians in a large-scale study. Objective The purpose of this study was to compare the accuracies of CHADS₂ and CHA₂DS₂-VASc scores in predicting ischemic stroke in Chinese patients. Methods This study used the National Health Insurance Research Database in Taiwan. A total of 186,570 AF patients without antithrombotic therapies were selected as the study cohort. The clinical end-point was occurrence of ischemic stroke. Results During follow-up of 3.4 ± 3.7 years, 23,723 patients (12.7%) experienced ischemic stroke. The CHA₂DS₂-VASc score performed better than CHADS₂ score in predicting ischemic stroke assessed by c-indexes (0.698 vs 0.659, P <.0001). Among 25,286 patients with a CHADS₂ score of 0, the CHA₂DS₂-VASc score ranged from 0 to 3, and the annual stroke rate ranged from 1.15% to 4.47%. Compared to patients with a CHA₂DS₂-VASc score of 0, the hazard ratio of ischemic stroke for patients with a CHA₂DS₂-VASc score of 3 was 3.998. Conclusion Patients with a CHADS₂ score of 0 were not necessarily "low risk," and the annual stroke rate can be as high as 4.47% when patients were further stratified by the CHA₂DS₂-VASc score. In contrast, patients with a CHA₂DS₂-VASc score of 0 had a truly low risk of ischemic stroke, with an annual stroke rate around 1.15%. As with Caucasians, the CHA₂DS₂-VASc score should be used for stroke risk stratification in Asians.