Background: The objective of this study was to evaluate the added predictive ability of the CHA(2)DS(2)VASc prediction rule for stroke and death in a nonanticoagulated population of patients with atrial fibrillation.
Methods and results: We included 1603 nonanticoagulated patients with incident atrial fibrillation from a Danish prospective cohort study of 57 053 middle-aged men and women. The Net Reclassification Improvement was calculated as a measure to estimate any overall improvement in reclassification with the CHA(2)DS(2)VASc sore as an alternative to the CHADS(2) score. After 1-year follow-up, crude incidence rates were 3.4 per 100 person-years for stroke and 13.6 for death. After a mean follow-up of 5.4 years (± 3.7 years), the crude incidence rates for stroke and death were 1.9 and 5.6, respectively. During the entire observation period, the c-statistics and negative predictive values were similar for both risk scores. The Net Reclassification Improvement analysis showed that 1 of 10 reclassified atrial fibrillation patients would have been upgraded correctly using the CHA(2)DS(2)VASc score.
Conclusions: Both the CHADS(2) as well as the CHA(2)DS(2)VASc risk score can exclude a large proportion of patients from having high risk of stroke or death. However, using the CHA(2)DS(2)VASc risk score, fewer patients will fulfill the criterion for low risk (and are truly low risk for thromboembolism). For every 10 extra patients transferred to the treatment group at 5 years, using the CHA(2)DS(2)VASc risk score, 1 patient would have had a stroke that might have been avoided with effective treatment.