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.

Funding: This work was supported by the Aarne Koskelo Foundation, The Finnish Foundation for Cardiovascular Research, The Finnish State Research funding, and Helsinki and Uusimaa Hospital District research fund.