Modified CHA2DS2-VASc Risk Score for Asian AF Patients
Does a modified CHA2DS2-VASc risk score with a broader age risk group work better for Asian patients than the traditional CHA2DS2-VASc risk score?
The authors used the Taiwan National Health Insurance Research Database of 224,866 newly diagnosed patients with atrial fibrillation (AF) between 1996 and 2006. The authors calculated the traditional CHA2DS2-VASc score (1 point for age 64-74) and a modified CHA2DS2-VASc score (1 point for age 50-74). Stroke risk was calculated based on 124,271 patients without antithrombotic use. The two risk scores were compared using C indexes based on the receiver operator curve (ROC) and by the net reclassification index. Net clinical benefit for use of warfarin or antiplatelet therapy was calculated using a weighting factor for intracranial hemorrhage.
During a follow-up of 538,653 years, 21,008 patients experienced an ischemic stroke. The C indexes were 0.689 (95% confidence interval [CI], 0.684-0.694) for CHA2DS2-VASc score and 0.708 (95% CI, 0.703-0.712) for the modified CHA2DS2-VASc score (p < 0.0001). The modified CHA2DS2-VASc score improved the net reclassification index by 3.39% (95% CI, 2.16-4.59%; p < 0.0001) as compared to the traditional CHA2DS2-VASc score. For patients with a CHA2DS2-VASc score of 0 (male) or 1 (female) who also had a modified CHA2DS2-VASc score of 1 (male) or 2 (female) based on the broader age category, use of warfarin as compared to no antithrombotic therapy was associated with a lower risk of ischemic stroke (adjusted hazard ratio [aHR], 0.70; 95% CI, 0.59-0.84; p < 0.001) without an increased risk of intracranial hemorrhage (aHR, 0.95; 95% CI, 0.61-1.46; p = 0.804). Net clinical benefit favored warfarin therapy over no antithrombotic therapy for all relative weighting factors of intracranial hemorrhage.
The authors concluded that among Asian AF patients, use of a modified CHA2DS2-VASc score (broader age risk group) better predicted ischemic stroke risk than a traditional CHA2DS2-VASc score.
Observational studies have previously noted a higher rate of stroke among lowest-risk Asian AF patients than in other ethnic populations. For that reason, the authors proposed a modified CHA2DS2-VASc score where patients ages 60-74 years received 1 point (as compared to 65-74 years in the traditional score). This effectively increases the number of patients with AF who are recommended for anticoagulant therapy based on multiple society guidelines. While observational studies comparing treated and nontreated AF patients always raise question of selection bias, this analysis supports the use of a modified CHA2DS2-VASc score for stroke risk stratification and net clinical benefit for warfarin therapy in the patients ages 50-64 years, who previously might not have received treatment. How well this modified risk stratification score works in other (non-Taiwanese) populations and in Asian American populations remains to be tested.
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