CHADS2 Calculator for Atrial Fibrillation

Evaluates ischemic stroke risk in patients with atrial fibrillation

Criteria Poss. Point
Congestive heart failure
The original manuscript required a 'recent' hospitalization for CHF, but most clinicians use any history of CHF or LV dysfunction as adequate criteria
Includes any history of a hypertension diagnosis, regardless of severity
Age 75 years or older
Diabetes mellitus
Includes any history of a diabetes diagnosis, regardless of severity
Stroke or TIA
Includes any history of cerebral ischemia
Press 'Calculate' to view calculation results.

About This Calculator

CHADS2 was designed as a scoring system to classify the risk of stroke in patients with atrial fibrillation. Prior to the study,2 there were conflicting data regarding independent risk factors and their importance in predicting the risk of stroke.

CHADS2 was developed from an independent registry of Medicare-aged patients with non-rheumatic atrial fibrillation who were not given warfarin at hospital discharge. Due to the constraints of the database, the study only included patients aged 65 to 95 years and was retrospective in data collection and analysis, relying on Medicare claims to assist with study endpoints.

CHADS2 Score and Stroke Risk

Each increase in CHADS2 was shown to predict ischemic stroke rate per year in a linear fashion:

Discrimination of Risk Factor Severity

At the expense of bedside simplicity, the CHADS2 system is unable to account for higher severity of illness with each risk factor considered. As an example, poorly controlled hypertension and diabetes have equal weight to that of a controlled patient. For this reason, it is important for clinicians to use the scoring system as a guide, not as an absolute answer.

Female Gender

Previous scoring systems used a combination of both age > 75 years AND female sex as a risk factor. In the CHADS2 system, age was preserved as a risk factor but female sex was discarded. Given the strong evidence regarding female sex and a higher risk of stroke, sex was added to the more contemporary CHA2DS2-VASC classification system.

References and Additional Reading

  1. Guyatt GH, Akl EA, Crowther M, et al. Executive summary: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 Suppl):7S-47S. PMID 22315257.
  2. Gage BF, Waterman AD, Shannon W, et al. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA. 2001;285(22):2864-70. PMID 11401607.


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Updated Nov 10, 2018
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