CHADS2 Score For Atrial Fibrillation Stroke Risk

Predicts risk of ischemic events caused by thromboembolism in patients with atrial fibrillation.

In the text below the calculator there is more information about the score interpretation and about the original study.

The CHADS2 score evaluates the risk of a thromboembolic ischemic event (in the following year) in patients diagnosed with non-valvular atrial fibrillation and stratifies patients in a low, intermediate or high risk group.

The scoring system can be administered at the bedside as it consists in patient history of CHF, hypertension or diabetes mellitus and in whether the patient has had, in the past, symptoms characteristic of TIA or stroke.

The AF patient is classed, according to the CHADS2 in a risk group. The final score is also associated with a 1-year stroke risk in percentage:

CHADS2 Risk group Stroke risk
0 Low 1.90%
1 Intermediate 2.80%
2 Intermediate 4%
3 High 5.90%
4 High 8.50%
5 High 12.50%
6 High 18.20%


Congestive heart failure history


Hypertension history


Age above 75 years


Diabetes mellitus history


Stroke or TIA symptoms previously

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CHADS2 explained

The CHADS2 score predicts the 1-year risk of ischemic stroke in patients with non-valvular atrial fibrillation who are not under anticoagulation treatment.

The score stratifies patients in risk groups and improves decision making related to the choice of most appropriate antithrombotic or antiplatelet therapy.

There are 5 criteria assessed as described below. The presence of either weighs one or two points (stroke or TIA symptoms) in the final score.

The name of the tool, CHADS2, is actually the acronym of the items in it with the mention of double points for the last item.

CHADS2 items Description
Congestive heart failure history History of previous inadequacy in the heart pump function can show a progressive disease that impairs the normal function.
Hypertension history Personal or family recurrence of high blood pressure (SBP above 140 mmHg).
Age above 75 Age as a risk factor in both stroke and other heart conditions.
Diabetes mellitus history DM as risk factor for stroke.
Stroke or TIA symptoms previously Personal history of associated symptoms.

There is also a newer, improved version of the score, the CHA2DS2-VASc, that was deemed to be more accurate than the initial score, especially in low risk patients.


Score interpretation

As the CHADS2 increases, the annual risk of ischemic stroke increases proportionally.

The following table introduces the group of thromboembolic event and the stroke risks in percentage, for each result, from 0 to 6.

CHADS2 Risk group Stroke risk
0 Low 1.90%
1 Intermediate 2.80%
2 Intermediate 4%
3 High 5.90%
4 High 8.50%
5 High 12.50%
6 High 18.20%

Some physicians use the above guidelines in terms of risk group whilst others consider that if the last item “Stroke or TIA symptoms previously” is marked as positive, the patients should be placed in the high risk group, even if the total score would class them as low or intermediate risk.

Patients with scores above 2 are considered to be at significant risk of thromboembolic events. These patients should be started on warfarin whilst being monitored for bleeding risk.

Patients with lower scores (0 or 1) are deemed low risk and can be administered aspirin as first choice antithrombotic therapy.

According to studies, less than 7% of patients with non-valvular atrial fibrillation, aged between 65 and 95, are classed as low risk.

If following the administration of the score, anticoagulation therapy is recommended (because the patient is at risk of ischemic events), the application of a bleeding risk score like HAS-BLED can help clinicians consider the advantages and disadvantages of this option.


About the study

The 2004 study by Gage et al. is based on data from a multicentre trial:

■ Atrial Fibrillation, Aspirin, Anticoagulation I study [AFASAK-1];


■ European Atrial Fibrillation Trial;

■ Primary Prevention of Arterial Thromboembolism in patients with nonrheumatic Atrial Fibrillation in primary care study;

■ Stroke Prevention and Atrial Fibrillation [SPAF]-III high risk or SPAF-III low risk.

Data from 2,580 subjects with nonvalvular AF who were prescribed aspirin was analysed. During the duration of the study (4,887 patient-years of aspirin therapy), 207 ischemic strokes occurred.

The main difference in the prediction of most stroke risk models tested was in their high variability in the number of patients categorized as low and high risk.

The CHADS2 model successfully identified patients with AF who were at high risk of stroke (5.3 strokes per 100 patient-years).

The administration of the score supports the initiation of antithrombotic prophylaxis in eligible patients.


Original source

Gage BF, van Walraven C, Pearce L, Hart RG, Koudstaal PJ, Boode BS, Petersen P. Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin. Circulation. 2004; 110(16):2287-92.


Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ. Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation. JAMA. 2001; 285(22):2864-70.

Other references

1. Singer DE, Albers GW, Dalen JE, Fang MC, Go AS, Halperin JL, Lip GYH, Manning WJ. Antithrombotic therapy in atrial fibrillation: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest. 2008; 133(6 Suppl):546S-592S.

2. Olesen JB, Torp-Pedersen C, Hansen ML, Lip GY. 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. Thromb Haemost. 2012; 107(6):1172-9.

Specialty: Cardiology

System: Cardiovascular

Objective: Risk Prediction

Type: Score

No. Of Items: 5

Year Of Study: 2004

Abbreviation: CHADS2

Article By: Denise Nedea

Published On: June 27, 2017

Last Checked: June 27, 2017

Next Review: June 27, 2023