Validation of risk stratification schemes for predicting stroke and thromboembolism in patients with atrial fibrillation: nationwide cohort study

Jonas Bjerring Olesen, Gregory Y H Lip, Morten Lock Hansen, Peter Riis Hansen, Janne Schurmann Tolstrup, Jesper Lindhardsen, Christian Selmer, Ole Ahlehoff, Anne-Marie Schjerning Olsen, Gunnar Hilmar Gislason, Christian Torp-Pedersen, Jonas Bjerring Olesen, Gregory Y H Lip, Morten Lock Hansen, Peter Riis Hansen, Janne Schurmann Tolstrup, Jesper Lindhardsen, Christian Selmer, Ole Ahlehoff, Anne-Marie Schjerning Olsen, Gunnar Hilmar Gislason, Christian Torp-Pedersen

Abstract

Objectives: To evaluate the individual risk factors composing the CHADS(2) (Congestive heart failure, Hypertension, Age ≥ 75 years, Diabetes, previous Stroke) score and the CHA(2)DS(2)-VASc (CHA(2)DS(2)-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 CHADS(2) and 0.78 (0.58 to 1.04) with CHA(2)DS(2)-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 CHADS(2) and 2.01 (1.70 to 2.36) with CHA(2)DS(2)-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 CHADS(2) and 0.888 (0.875 to 0.900) with CHA(2)DS(2)-VASc.

Conclusions: The risk associated with a specific risk stratification score depended on the risk factors composing the score. CHA(2)DS(2)-VASc performed better than CHADS(2) in predicting patients at high risk, and those categorised as low risk by CHA(2)DS(2)-VASc were truly at low risk for thromboembolism.

Conflict of interest statement

Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4788060/bin/olej809822.f1_default.jpg
Fig 1 Flow chart of study population
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4788060/bin/olej809822.f2_default.jpg
Fig 2 Kaplan-Meier estimate of probability of remaining free of thromboembolism with CHADS2 score 0 and 1. Only patients with CHADS2 scores 0 and 1 were included, and patients were censored at death for causes other than thromboembolism
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4788060/bin/olej809822.f3_default.jpg
Fig 3 Kaplan-Meier estimate of probability of remaining free of thromboembolism with CHA2DS2-VASc score 0 and 1. Only patients with CHA2DS2-VASc scores 0 and 1 were included, and patients were censored at death for causes other than thromboembolism

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