title: The value of the CHA2DS2-VASc score for refining stroke risk stratification in patients with atrial fibrillation with a CHADS2 score 0-1: a nationwide cohort study.
abstract: North American and European guidelines on atrial fibrillation (AF) are conflicting regarding the classification of patients at low/intermediate risk of stroke. We aimed to investigate if the CHA2DS2-VASc score improved risk stratification of AF patients with a CHADS2 score of 0-1. Using individual-level-linkage of nationwide Danish registries 1997-2008, we identified patients discharged with AF having a CHADS2 score of 0-1 and not treated with vitamin K antagonist or heparin. In patients with a CHADS2 score of 0, 1, and 0-1, rates of stroke/ thromboembolism were determined according to CHA2DS2-VASc score, and the risk associated with increasing CHA2DS2-VASc score was estimated in Cox regression models adjusted for year of inclusion and antiplatelet therapy. The value of adding the extra CHA2DS2-VASc risk factors to the CHADS2 score was evaluated by c-statistics, Net Reclassification Improvement (NRI) and Integrated Discrimination Improvement (IDI). We included 47,576 patients with a CHADS2 score of 0-1, from these 7,536 (15.8%) were CHA2DS2-VASc score=0, 10,062 (21.2%) were CHA2DS2-VASc score=1, 14,310 (30.1%) were CHA2DS2-VASc score=2, 14,188 (29.8%) were CHA2DS2-VASc score=3, and 1,480 (3.1%) were CHA2DS2-VASc score=4. Of the cohort with a CHADS2 score of 0-1, the stroke/thromboembolism rate per 100 person-years increased with increasing CHA2DS2-VASc score (95% confidence interval): 0.84 (0.65-1.08), 1.79 (1.53-2.09), 3.67 (3.34-4.03), 5.75 (5.33-6.21), and 8.18 (6.68-10.02) at one year follow-up with CHA2DS2-VASc scores of 0, 1, 2, 3, and 4, respectively. Patients with a CHADS2 score=0 were not all 'low risk', with one-year event rates ranging from 0.84 (CHA2DS2-VASc score=0) to 3.2 (CHA2DS2-VASc score=3). Results from Cox regression analyses, NRI, and IDI confirmed the improved predictive ability of the CHA2DS2-VASc score in the AF patients who have a CHADS2 score of 0-1. In conclusion, the CHA2DS2-VASc provides critical information on risk of stroke in AF patients with a CHADS2 score of 0-1 that can aid a decision of using anticoagulation. Even in patients categorised as 'low risk' using a CHADS2 score=0, the CHA2DS2-VASc score significantly improved the predictive value of the CHADS2 score alone and a CHA2DS2-VASc score=0 could clearly identify 'truly low risk' subjects. Use of the CHA2DS2-VASc score would significantly improve classification of AF patients at low and intermediate risk of stroke, compared to the commonly used CHADS2 score.
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Gentofte, Hellerup, Denmark. jo@heart.dk
authors.forename: Jonas Bjerring
authors.initials: JB
authors.lastname: Olesen
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
authors.forename: Morten Lock
authors.initials: ML
authors.lastname: Hansen
authors.forename: Gregory Y H
authors.initials: GY
authors.lastname: Lip
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000188:drug therapy / Q000453:epidemiology*; D015331:Cohort Studies; D003661:Decision Support Techniques; D003718:Denmark / Q000453:epidemiology; D016002:Discriminant Analysis; D018450:Disease Progression; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D016016:Proportional Hazards Models; D012042:Registries; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000517:prevention & control; D013923:Thromboembolism / Q000453:epidemiology* / Q000517:prevention & control; D013997:Time Factors
chemical_list: D000925:Anticoagulants