Objectives To evaluate the individual risk factors
composing the CHADS2 (Congestive heart failure,
Hypertension, Age=75 years, Diabetes, previous Stroke)
score and the CHA2DS2-VASc (CHA2DS2-Vascular disease,
Age 65-74 years, Sex category) score and to calculate the
capability of the schemes to predict thromboembolism.
Design Registry based cohort study.
Setting Nationwide data on patients admitted to hospital
with atrial fibrillation.
Population All patients with atrial fibrillation not treated
with vitamin K antagonists in Denmark in the period 1997-
2006.
Main outcome measures Stroke and thromboembolism.
Results Of 121 280 patients with non-valvular atrial
fibrillation, 73 538 (60.6%) fulfilled the study inclusion
criteria. In patients at “low risk” (score=0), the rate of
thromboembolism per 100 person years was 1.67 (95%
confidence interval 1.47 to 1.89) with CHADS2 and 0.78
(0.58 to 1.04) with CHA2DS2-VASc at one year’s follow-up.
In patients at “intermediate risk” (score=1), this rate was
4.75 (4.45 to 5.07) with CHADS2 and 2.01 (1.70 to 2.36)
with CHA2DS2-VASc. The rate of thromboembolism
depended on the individual risk factors composing the
scores, and both schemes underestimated the risk
associated with previous thromboembolic events. When
patients were categorised into low, intermediate, and
high risk groups, C statistics at 10 years’ follow-up were
0.812 (0.796 to 0.827) with CHADS2 and 0.888 (0.875 to
0.900) with CHA2DS2-VASc.
Conclusions The risk associated with a specific risk
stratification score depended on the risk factors
composing the score. CHA2DS2-VASc performed better
than CHADS2 in predicting patients at high risk, and those
categorised as low risk by CHA2DS2-VASc were truly at low
risk for thromboembolism.