Comparing CHA2DS2-VA and CHA2DS2-VASc scores for stroke risk stratification in patients with atrial fibrillation: a temporal trends analysis from the retrospective Finnish AntiCoagulation in Atrial Fibrillation (FinACAF) cohort

Background Contemporary data have shown a decrease in the ischaemic stroke risk associated with female sex in patients with atrial fibrillation (AF). We evaluated temporal trends in the predictive value of a non-sex CHA2DS2-VASc risk score (ie. CHA2DS2-VA). Methods The FinACAF study covers all patients with incident AF between 2007 and 2018 in Finland from all levels of care. The CHA2DS2-VA score was compared with the CHA2DS2-VASc using continuous and category-based net reclassification indices (NRIs), integrated discrimination improvement (IDI), c-statistics and decision curve analyses. Findings We identified 144,879 anticoagulant naïve patients with new-onset AF between 2007 and 2018 (49.9% women; mean age 72.1 years), of whom 3936 (2.7%) experienced ischaemic stroke during one-year follow-up. Based on both continuous and category-based NRIs, the CHA2DS2-VA score was inferior to the CHA2DS2-VASc in the early years (−0.333 (95% CI −0.411 to −0.261) and −0.118 (95% CI −0.137 to −0.099), respectively). However, the differences attenuated over time, and by the end of the study period, the continuous NRI became non-significant (−0.093 (95% CI −0.165 to 0.032)), whereas the category-based NRI reversed in favor of the CHA2DS2-VA (0.070 (95% CI 0.048–0.087)). The IDI was non-significant in early years (0.0009 (95% CI −0.0024 to 0.0037)), but over time became statistically significant in favor of the CHA2DS2-VA score (0.0022 (95% CI 0.0001–0.0044)). The Cox models fitted with the CHA2DS2-VA and the CHA2DS2-VASc scores exhibited comparable discriminative capability in the beginning of the study (p-value 0.63), but over time marginal differences in favor of the CHA2DS2-VA score emerged (p-value 0.0002). Interpretation In 2007–2008 (when females had higher AF-related stroke risks than males), the CHA2DS2-VASc score outperformed the CHA2DS2-VA score, but the initial differences between the scores attenuated over time. By the end of the study period in 2017–2018 (with limited/no sex differences in AF-related stroke), there was marginal superiority for the CHA2DS2-VA score.