Validation of Risk Scoring System Excluding Female Sex From CHA2DS2-VASc in Japanese Patients With Nonvalvular Atrial Fibrillation

Background: Because the current Japanese guideline recommends CHADS(2) score-based risk stratification in nonvalvular atrial fibrillation (NVAF) patients and does not list female sex as a risk for thromboembolic events, we designed the present study to compare the CHA(2)DS(2)-VASc and CHA(2)DS(2)-VA scores in the J-RHYTHM Registry. Methods and Results: We prospectively assessed the incidence of thromboembolic events for 2 years in 997 NVAF patients without warfarin treatment (age 68+/-12 years, 294 females). The predictive value of the CHA(2)DS(2)VASc and CHA(2)DS(2)-VA scores for thromboembolic events was evaluated by c-statistic difference and net reclassification improvement (NRI). Thromboembolic events occurred in 7/294 females (1.2%/year) and 23/703 males (1.6%/year) (odds ratio 0.72 for female to male, 95% confidence interval (CI) 0.28-1.62, P=0.44). No sex difference was found in patient groups stratified by CHA(2)DS(2)-VASc and CHA(2)DS(2)-VA scores. There were significant c-statistic difference (0.029, Z=2.3, P=0.02) and NRI (0.11, 95% CI 0.01-0.20, P=0.02), with the CHA(2)DS(2)-VA score being superior to the CHA(2)DS(2)-VASc score. In patients with CHA(2)DS(2)-VASc scores 0 and 1 (n=374), there were markedly significant c-statistic difference (0.053, Z=6.6, P<0.0001) and NRI (0.11, 95% CI 0.07-0.14, P<0.0001), again supporting superiority of CHA(2)DS(2)-VA to CHA(2)DS(2)-VASc score. Conclusions: In Japanese NVAF patients, the CHA(2)DS(2)-VA score, a risk scoring system excluding female sex from CHA(2)DS(2)-VASc, may be more useful in risk stratification for thromboembolic events than CHA2DS2-VASc score, especially in identifying truly low-risk patients.