The CHADS2 score: Stroke risk in atrial fibrillation [Classics Series]

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1. The CHADS2 index is an accurate predictor of stroke in patients with non-rheumatic atrial fibrillation.

2. CHADS2 scores can be used to aid decisions regarding the need for anti-thrombotic therapy.

Original Date of Publication: June 13, 2001

Study Rundown: The CHADS2 index combined risk factors identified by the Atrial Fibrillation Investigators (AFI) and the Stroke Prevention and Atrial Fibrillation (SPAF) investigators to create a new clinical prediction model for stroke in patients with atrial fibrillation. This study validated the three tools and found that CHADS2 predicts stroke with greater accuracy than both the AFI and SPAF schemes. CHADS2 scores can be used to guide decisions regarding the need for anti-thrombotic therapy (i.e., aspirin for low-risk patients, warfarin for high-risk patients), particularly in identifying low-risk patients who may benefit from aspirin therapy. Strengths of the study include wide representation of regions within the United States and generalizability of results to frail, elderly patients. The CHADS2 index includes a limited set of risk factors for stroke and may neglect other important risk factors.

Please click to read the study in JAMA

In-Depth [randomized, controlled study]: This study, originally published in JAMA in 2001, evaluated the predictive accuracy of the AFI and SPAF stroke classification schemes, as well as the CHADS2 index, a new stroke-risk prediction model created by combining the AFI and SPAF schemes. CHADS2 is an acronym for the risk factors considered and their score value. One point is assigned for any of the following risk factors: recent congestive heart failure, hypertension, age ≥75 years, and diabetes mellitus. Two points were added if there is a history of stroke or transient ischemic attack.

Risk factor


Congestive heart failure




Age ≥75 years


Diabetes mellitus


Stroke or transient ischemic attack



The study included 1,733 patients between ages 65 to 95 years with non-rheumatic atrial fibrillation. Stroke rate increased by a factor of 1.5 for each 1-point increment in CHADS2 score (P<0.001) and the CHADS2 index was found to predict stroke with greater accuracy than both the AFI and SPAF schemes with a c statistic of 0.82.

CHADS2 score

Stroke rate per 100 patient-years















By Adrienne Cheung, Andrew Cheung, M.D.

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